Add ASCII video skill to creative category

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---
name: ascii-video
description: "Production pipeline for ASCII art video — any format. Converts video/audio/images/generative input into colored ASCII character video output (MP4, GIF, image sequence). Covers: video-to-ASCII conversion, audio-reactive music visualizers, generative ASCII art animations, hybrid video+audio reactive, text/lyrics overlays, real-time terminal rendering. Use when users request: ASCII video, text art video, terminal-style video, character art animation, retro text visualization, audio visualizer in ASCII, converting video to ASCII art, matrix-style effects, or any animated ASCII output."
---
# ASCII Video Production Pipeline
Full production pipeline for rendering any content as colored ASCII character video.
## Modes
| Mode | Input | Output | Read |
|------|-------|--------|------|
| **Video-to-ASCII** | Video file | ASCII recreation of source footage | `references/inputs.md` § Video Sampling |
| **Audio-reactive** | Audio file | Generative visuals driven by audio features | `references/inputs.md` § Audio Analysis |
| **Generative** | None (or seed params) | Procedural ASCII animation | `references/effects.md` |
| **Hybrid** | Video + audio | ASCII video with audio-reactive overlays | Both input refs |
| **Lyrics/text** | Audio + text/SRT | Timed text with visual effects | `references/inputs.md` § Text/Lyrics |
| **TTS narration** | Text quotes + TTS API | Narrated testimonial/quote video with typed text | `references/inputs.md` § TTS Integration |
## Stack
Single self-contained Python script per project. No GPU.
| Layer | Tool | Purpose |
|-------|------|---------|
| Core | Python 3.10+, NumPy | Math, array ops, vectorized effects |
| Signal | SciPy | FFT, peak detection (audio modes only) |
| Imaging | Pillow (PIL) | Font rasterization, video frame decoding, image I/O |
| Video I/O | ffmpeg (CLI) | Decode input, encode output segments, mux audio, mix tracks |
| Parallel | concurrent.futures / multiprocessing | N workers for batch/clip rendering |
| TTS | ElevenLabs API (or similar) | Generate narration clips for quote/testimonial videos |
| Optional | OpenCV | Video frame sampling, edge detection, optical flow |
## Pipeline Architecture (v2)
Every mode follows the same 6-stage pipeline. See `references/architecture.md` for implementation details, `references/scenes.md` for scene protocol, and `references/composition.md` for multi-grid composition and tonemap.
```
┌─────────┐ ┌──────────┐ ┌───────────┐ ┌──────────┐ ┌─────────┐ ┌────────┐
│ 1.INPUT │→│ 2.ANALYZE │→│ 3.SCENE_FN │→│ 4.TONEMAP │→│ 5.SHADE │→│ 6.ENCODE│
│ load src │ │ features │ │ → canvas │ │ normalize │ │ post-fx │ │ → video │
└─────────┘ └──────────┘ └───────────┘ └──────────┘ └─────────┘ └────────┘
```
1. **INPUT** — Load/decode source material (video frames, audio samples, images, or nothing)
2. **ANALYZE** — Extract per-frame features (audio bands, video luminance/edges, motion vectors)
3. **SCENE_FN** — Scene function renders directly to pixel canvas (`uint8 H,W,3`). May internally compose multiple character grids via `_render_vf()` + pixel blend modes. See `references/composition.md`
4. **TONEMAP** — Percentile-based adaptive brightness normalization with per-scene gamma. Replaces linear brightness multipliers. See `references/composition.md` § Adaptive Tonemap
5. **SHADE** — Apply post-processing `ShaderChain` + `FeedbackBuffer`. See `references/shaders.md`
6. **ENCODE** — Pipe raw RGB frames to ffmpeg for H.264/GIF encoding
## Creative Direction
**Every project should look and feel different.** The references provide a vocabulary of building blocks — don't copy them verbatim. Combine, modify, and invent.
### Aesthetic Dimensions to Vary
| Dimension | Options | Reference |
|-----------|---------|-----------|
| **Character palette** | Density ramps, block elements, symbols, scripts (katakana, Greek, runes, braille), dots, project-specific | `architecture.md` § Character Palettes |
| **Color strategy** | HSV (angle/distance/time/value mapped), discrete RGB palettes, monochrome, complementary, triadic, temperature | `architecture.md` § Color System |
| **Color tint** | Warm, cool, amber, matrix green, neon pink, sepia, ice, blood, void, sunset | `shaders.md` § Color Grade |
| **Background texture** | Sine fields, noise, smooth noise, cellular/voronoi, video source | `effects.md` § Background Fills |
| **Primary effects** | Rings, spirals, tunnel, vortex, waves, interference, aurora, ripple, fire | `effects.md` § Radial / Wave / Fire |
| **Particles** | Energy sparks, snow, rain, bubbles, runes, binary data, orbits, gravity wells | `effects.md` § Particle Systems |
| **Shader mood** | Retro CRT, clean modern, glitch art, cinematic, dreamy, harsh industrial, psychedelic | `shaders.md` § Design Philosophy |
| **Grid density** | xs(8px) through xxl(40px), mixed per layer | `architecture.md` § Grid System |
| **Font** | Menlo, Monaco, Courier, SF Mono, JetBrains Mono, Fira Code, IBM Plex | `architecture.md` § Font Selection |
| **Mirror mode** | None, horizontal, vertical, quad, diagonal, kaleidoscope | `shaders.md` § Mirror Effects |
| **Transition style** | Crossfade, wipe (directional/radial), dissolve, glitch cut | `shaders.md` § Transitions |
### Per-Section Variation
Never use the same config for the entire video. For each section/scene/quote:
- Choose a **different background effect** (or compose 2-3)
- Choose a **different character palette** (match the mood)
- Choose a **different color strategy** (or at minimum a different hue)
- Vary **shader intensity** (more bloom during peaks, more grain during quiet)
- Use **different particle types** if particles are active
### Project-Specific Invention
For every project, invent at least one of:
- A custom character palette matching the theme
- A custom background effect (combine/modify existing ones)
- A custom color palette (discrete RGB set matching the brand/mood)
- A custom particle character set
## Workflow
### Step 1: Determine Mode and Gather Requirements
Establish with user:
- **Input source** — file path, format, duration
- **Mode** — which of the 6 modes above
- **Sections** — time-mapped style changes (timestamps → effect names)
- **Resolution** — default 1920x1080 @ 24fps; GIFs typically 640x360 @ 15fps
- **Style direction** — dense/sparse, bright/dark, chaotic/minimal, color palette
- **Text/branding** — easter eggs, overlays, credits, themed character sets
- **Output format** — MP4 (default), GIF, PNG sequence
### Step 2: Detect Hardware and Set Quality
Before building the script, detect the user's hardware and set appropriate defaults. See `references/optimization.md` § Hardware Detection.
```python
hw = detect_hardware()
profile = quality_profile(hw, target_duration, user_quality_pref)
log(f"Hardware: {hw['cpu_count']} cores, {hw['mem_gb']:.1f}GB RAM")
log(f"Render: {profile['vw']}x{profile['vh']} @{profile['fps']}fps, {profile['workers']} workers")
```
Never hardcode worker counts, resolution, or CRF. Always detect and adapt.
### Step 3: Build the Script
Write as a single Python file. Major components:
1. **Hardware detection + quality profile** — see `references/optimization.md`
2. **Input loader** — mode-dependent; see `references/inputs.md`
3. **Feature analyzer** — audio FFT, video luminance, or pass-through
4. **Grid + renderer** — multi-density character grids with bitmap cache; `_render_vf()` helper for value/hue field → canvas
5. **Character palettes** — multiple palettes chosen per project theme; see `references/architecture.md`
6. **Color system** — HSV + discrete RGB palettes as needed; see `references/architecture.md`
7. **Scene functions** — each returns `canvas (uint8 H,W,3)` directly. May compose multiple grids internally via pixel blend modes. See `references/scenes.md` + `references/composition.md`
8. **Tonemap** — adaptive brightness normalization with per-scene gamma; see `references/composition.md`
9. **Shader pipeline**`ShaderChain` + `FeedbackBuffer` per-section config; see `references/shaders.md`
10. **Scene table + dispatcher** — maps time ranges to scene functions + shader/feedback configs; see `references/scenes.md`
11. **Parallel encoder** — N-worker batch clip rendering with ffmpeg pipes
12. **Main** — orchestrate full pipeline
### Step 4: Handle Critical Bugs
#### Font Cell Height (macOS Pillow)
`textbbox()` returns wrong height. Use `font.getmetrics()`:
```python
ascent, descent = font.getmetrics()
cell_height = ascent + descent # correct
```
#### ffmpeg Pipe Deadlock
Never use `stderr=subprocess.PIPE` with long-running ffmpeg. Redirect to file:
```python
stderr_fh = open(err_path, "w")
pipe = subprocess.Popen(cmd, stdin=subprocess.PIPE, stdout=subprocess.DEVNULL, stderr=stderr_fh)
```
#### Brightness — Use `tonemap()`, Not Linear Multipliers
ASCII on black is inherently dark. This is the #1 visual issue. **Do NOT use linear `* N` brightness multipliers** — they clip highlights and wash out the image. Instead, use the **adaptive tonemap** function from `references/composition.md`:
```python
def tonemap(canvas, gamma=0.75):
"""Percentile-based adaptive normalization + gamma. Replaces all brightness multipliers."""
f = canvas.astype(np.float32)
lo = np.percentile(f, 1) # black point (1st percentile)
hi = np.percentile(f, 99.5) # white point (99.5th percentile)
if hi - lo < 1: hi = lo + 1
f = (f - lo) / (hi - lo)
f = np.clip(f, 0, 1) ** gamma # gamma < 1 = brighter mids
return (f * 255).astype(np.uint8)
```
Pipeline ordering: `scene_fn() → tonemap() → FeedbackBuffer → ShaderChain → ffmpeg`
Per-scene gamma overrides for destructive effects:
- Default: `gamma=0.75`
- Solarize scenes: `gamma=0.55` (solarize darkens above-threshold pixels)
- Posterize scenes: `gamma=0.50` (quantization loses brightness range)
- Already-bright scenes: `gamma=0.85`
Additional brightness best practices:
- Dense animated backgrounds — never flat black, always fill the grid
- Vignette minimum clamped to 0.15 (not 0.12)
- Bloom threshold lowered to 130 (not 170) so more pixels contribute to glow
- Use `screen` blend mode (not `overlay`) when compositing dark ASCII layers — overlay squares dark values: `2 * 0.12 * 0.12 = 0.03`
#### Font Compatibility
Not all Unicode characters render in all fonts. Validate palettes at init:
```python
for c in palette:
img = Image.new("L", (20, 20), 0)
ImageDraw.Draw(img).text((0, 0), c, fill=255, font=font)
if np.array(img).max() == 0:
log(f"WARNING: char '{c}' (U+{ord(c):04X}) not in font, removing from palette")
```
### Step 4b: Per-Clip Architecture (for segmented videos)
When the video has discrete segments (quotes, scenes, chapters), render each as a separate clip file. This enables:
- Re-rendering individual clips without touching the rest (`--clip q05`)
- Faster iteration on specific sections
- Easy reordering or trimming in post
```python
segments = [
{"id": "intro", "start": 0.0, "end": 5.0, "type": "intro"},
{"id": "q00", "start": 5.0, "end": 12.0, "type": "quote", "qi": 0, ...},
{"id": "t00", "start": 12.0, "end": 13.5, "type": "transition", ...},
{"id": "outro", "start": 208.0, "end": 211.6, "type": "outro"},
]
from concurrent.futures import ProcessPoolExecutor, as_completed
with ProcessPoolExecutor(max_workers=hw["workers"]) as pool:
futures = {pool.submit(render_clip, seg, features, path): seg["id"]
for seg, path in clip_args}
for fut in as_completed(futures):
fut.result()
```
CLI: `--clip q00 t00 q01` to re-render specific clips, `--list` to show segments, `--skip-render` to re-stitch only.
### Step 5: Render and Iterate
Performance targets per frame:
| Component | Budget |
|-----------|--------|
| Feature extraction | 1-5ms |
| Effect function | 2-15ms |
| Character render | 80-150ms (bottleneck) |
| Shader pipeline | 5-25ms |
| **Total** | ~100-200ms/frame |
**Fast iteration**: render single test frames to check brightness/layout before full render:
```python
canvas = render_single_frame(frame_index, features, renderer)
Image.fromarray(canvas).save("test.png")
```
**Brightness verification**: sample 5-10 frames across video, check `mean > 8` for ASCII content.
## References
| File | Contents |
|------|----------|
| `references/architecture.md` | Grid system, font selection, character palettes (library of 20+), color system (HSV + discrete RGB), `_render_vf()` helper, compositing, v2 effect function contract |
| `references/inputs.md` | All input sources: audio analysis, video sampling, image conversion, text/lyrics, TTS integration (ElevenLabs, voice assignment, audio mixing) |
| `references/effects.md` | Effect building blocks: 12 value field generators (`vf_sinefield` through `vf_noise_static`), 8 hue field generators (`hf_fixed` through `hf_plasma`), radial/wave/fire effects, particles, composing guide |
| `references/shaders.md` | 38 shader implementations (geometry, channel, color, glow, noise, pattern, tone, glitch, mirror), `ShaderChain` class, full `_apply_shader_step()` dispatch, audio-reactive scaling, transitions, tint presets |
| `references/composition.md` | **v2 core**: pixel blend modes (20 modes with implementations), multi-grid composition, `_render_vf()` helper, adaptive `tonemap()`, per-scene gamma, `FeedbackBuffer` with spatial transforms, `PixelBlendStack` |
| `references/scenes.md` | **v2 scene protocol**: scene function contract, `Renderer` class, `SCENES` table structure, `render_clip()` loop, beat-synced cutting, parallel rendering + pickling constraints, 4 complete scene examples, scene design checklist |
| `references/troubleshooting.md` | NumPy broadcasting traps, blend mode pitfalls, multiprocessing/pickling issues, brightness diagnostics, ffmpeg deadlocks, font issues, performance bottlenecks, common mistakes |
| `references/optimization.md` | Hardware detection, adaptive quality profiles (draft/preview/production/max), CLI integration, vectorized effect patterns, parallel rendering, memory management |

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# Architecture Reference
## Grid System
### Multi-Density Grids
Pre-initialize multiple grid sizes. Switch per section for visual variety.
| Key | Font Size | Grid (1920x1080) | Use |
|-----|-----------|-------------------|-----|
| xs | 8 | 400x108 | Ultra-dense data fields |
| sm | 10 | 320x83 | Dense detail, rain, starfields |
| md | 16 | 192x56 | Default balanced, transitions |
| lg | 20 | 160x45 | Quote/lyric text (readable at 1080p) |
| xl | 24 | 137x37 | Short quotes, large titles |
| xxl | 40 | 80x22 | Giant text, minimal |
**Grid sizing for text-heavy content**: When displaying readable text (quotes, lyrics, testimonials), use 20px (`lg`) as the primary grid. This gives 160 columns -- plenty for lines up to ~50 chars centered. For very short quotes (< 60 chars, <= 3 lines), 24px (`xl`) makes them more impactful. Only init the grids you actually use -- each grid pre-rasterizes all characters which costs ~0.3-0.5s.
Grid dimensions: `cols = VW // cell_width`, `rows = VH // cell_height`.
### Font Selection
Don't hardcode a single font. Choose fonts to match the project's mood. Monospace fonts are required for grid alignment but vary widely in personality:
| Font | Personality | Platform |
|------|-------------|----------|
| Menlo | Clean, neutral, Apple-native | macOS |
| Monaco | Retro terminal, compact | macOS |
| Courier New | Classic typewriter, wide | Cross-platform |
| SF Mono | Modern, tight spacing | macOS |
| Consolas | Windows native, clean | Windows |
| JetBrains Mono | Developer, ligature-ready | Install |
| Fira Code | Geometric, modern | Install |
| IBM Plex Mono | Corporate, authoritative | Install |
| Source Code Pro | Adobe, balanced | Install |
**Font detection at init**: probe available fonts and fall back gracefully:
```python
import platform
def find_font(preferences):
"""Try fonts in order, return first that exists."""
for name, path in preferences:
if os.path.exists(path):
return path
raise FileNotFoundError(f"No monospace font found. Tried: {[p for _,p in preferences]}")
FONT_PREFS_MACOS = [
("Menlo", "/System/Library/Fonts/Menlo.ttc"),
("Monaco", "/System/Library/Fonts/Monaco.ttf"),
("SF Mono", "/System/Library/Fonts/SFNSMono.ttf"),
("Courier", "/System/Library/Fonts/Courier.ttc"),
]
FONT_PREFS_LINUX = [
("DejaVu Sans Mono", "/usr/share/fonts/truetype/dejavu/DejaVuSansMono.ttf"),
("Liberation Mono", "/usr/share/fonts/truetype/liberation/LiberationMono-Regular.ttf"),
("Noto Sans Mono", "/usr/share/fonts/truetype/noto/NotoSansMono-Regular.ttf"),
("Ubuntu Mono", "/usr/share/fonts/truetype/ubuntu/UbuntuMono-R.ttf"),
]
FONT_PREFS = FONT_PREFS_MACOS if platform.system() == "Darwin" else FONT_PREFS_LINUX
```
**Multi-font rendering**: use different fonts for different layers (e.g., monospace for background, a bolder variant for overlay text). Each GridLayer owns its own font:
```python
grid_bg = GridLayer(find_font(FONT_PREFS), 16) # background
grid_text = GridLayer(find_font(BOLD_PREFS), 20) # readable text
```
### Collecting All Characters
Before initializing grids, gather all characters that need bitmap pre-rasterization:
```python
all_chars = set()
for pal in [PAL_DEFAULT, PAL_DENSE, PAL_BLOCKS, PAL_RUNE, PAL_KATA,
PAL_GREEK, PAL_MATH, PAL_DOTS, PAL_BRAILLE, PAL_STARS,
PAL_BINARY, PAL_MUSIC, PAL_BOX, PAL_CIRCUIT, PAL_ARROWS,
PAL_HERMES]: # ... all palettes used in project
all_chars.update(pal)
# Add any overlay text characters
all_chars.update("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789 .,-:;!?/|")
all_chars.discard(" ") # space is never rendered
```
### GridLayer Initialization
Each grid pre-computes coordinate arrays for vectorized effect math:
```python
class GridLayer:
def __init__(self, font_path, font_size):
self.font = ImageFont.truetype(font_path, font_size)
asc, desc = self.font.getmetrics()
bbox = self.font.getbbox("M")
self.cw = bbox[2] - bbox[0] # character cell width
self.ch = asc + desc # CRITICAL: not textbbox height
self.cols = VW // self.cw
self.rows = VH // self.ch
self.ox = (VW - self.cols * self.cw) // 2 # centering
self.oy = (VH - self.rows * self.ch) // 2
# Index arrays
self.rr = np.arange(self.rows, dtype=np.float32)[:, None]
self.cc = np.arange(self.cols, dtype=np.float32)[None, :]
# Polar coordinates (aspect-corrected)
cx, cy = self.cols / 2.0, self.rows / 2.0
asp = self.cw / self.ch
self.dx = self.cc - cx
self.dy = (self.rr - cy) * asp
self.dist = np.sqrt(self.dx**2 + self.dy**2)
self.angle = np.arctan2(self.dy, self.dx)
# Normalized (0-1 range) -- for distance falloff
self.dx_n = (self.cc - cx) / max(self.cols, 1)
self.dy_n = (self.rr - cy) / max(self.rows, 1) * asp
self.dist_n = np.sqrt(self.dx_n**2 + self.dy_n**2)
# Pre-rasterize all characters to float32 bitmaps
self.bm = {}
for c in all_chars:
img = Image.new("L", (self.cw, self.ch), 0)
ImageDraw.Draw(img).text((0, 0), c, fill=255, font=self.font)
self.bm[c] = np.array(img, dtype=np.float32) / 255.0
```
### Character Render Loop
The bottleneck. Composites pre-rasterized bitmaps onto pixel canvas:
```python
def render(self, chars, colors, canvas=None):
if canvas is None:
canvas = np.zeros((VH, VW, 3), dtype=np.uint8)
for row in range(self.rows):
y = self.oy + row * self.ch
if y + self.ch > VH: break
for col in range(self.cols):
c = chars[row, col]
if c == " ": continue
x = self.ox + col * self.cw
if x + self.cw > VW: break
a = self.bm[c] # float32 bitmap
canvas[y:y+self.ch, x:x+self.cw] = np.maximum(
canvas[y:y+self.ch, x:x+self.cw],
(a[:, :, None] * colors[row, col]).astype(np.uint8))
return canvas
```
Use `np.maximum` for additive blending (brighter chars overwrite dimmer ones, never darken).
### Multi-Layer Rendering
Render multiple grids onto the same canvas for depth:
```python
canvas = np.zeros((VH, VW, 3), dtype=np.uint8)
canvas = grid_lg.render(bg_chars, bg_colors, canvas) # background layer
canvas = grid_md.render(main_chars, main_colors, canvas) # main layer
canvas = grid_sm.render(detail_chars, detail_colors, canvas) # detail overlay
```
---
## Character Palettes
### Design Principles
Character palettes are the primary visual texture of ASCII video. They control not just brightness mapping but the entire visual feel. Design palettes intentionally:
- **Visual weight**: characters sorted by the amount of ink/pixels they fill. Space is always index 0.
- **Coherence**: characters within a palette should belong to the same visual family.
- **Density curve**: the brightness-to-character mapping is nonlinear. Dense palettes (many chars) give smoother gradients; sparse palettes (5-8 chars) give posterized/graphic looks.
- **Rendering compatibility**: every character in the palette must exist in the font. Test at init and remove missing glyphs.
### Palette Library
Organized by visual family. Mix and match per project -- don't default to PAL_DEFAULT for everything.
#### Density / Brightness Palettes
```python
PAL_DEFAULT = " .`'-:;!><=+*^~?/|(){}[]#&$@%" # classic ASCII art
PAL_DENSE = " .:;+=xX$#@\u2588" # simple 11-level ramp
PAL_MINIMAL = " .:-=+#@" # 8-level, graphic
PAL_BINARY = " \u2588" # 2-level, extreme contrast
PAL_GRADIENT = " \u2591\u2592\u2593\u2588" # 4-level block gradient
```
#### Unicode Block Elements
```python
PAL_BLOCKS = " \u2591\u2592\u2593\u2588\u2584\u2580\u2590\u258c" # standard blocks
PAL_BLOCKS_EXT = " \u2596\u2597\u2598\u2599\u259a\u259b\u259c\u259d\u259e\u259f\u2591\u2592\u2593\u2588" # quadrant blocks (more detail)
PAL_SHADE = " \u2591\u2592\u2593\u2588\u2587\u2586\u2585\u2584\u2583\u2582\u2581" # vertical fill progression
```
#### Symbolic / Thematic
```python
PAL_MATH = " \u00b7\u2218\u2219\u2022\u00b0\u00b1\u2213\u00d7\u00f7\u2248\u2260\u2261\u2264\u2265\u221e\u222b\u2211\u220f\u221a\u2207\u2202\u2206\u03a9" # math symbols
PAL_BOX = " \u2500\u2502\u250c\u2510\u2514\u2518\u251c\u2524\u252c\u2534\u253c\u2550\u2551\u2554\u2557\u255a\u255d\u2560\u2563\u2566\u2569\u256c" # box drawing
PAL_CIRCUIT = " .\u00b7\u2500\u2502\u250c\u2510\u2514\u2518\u253c\u25cb\u25cf\u25a1\u25a0\u2206\u2207\u2261" # circuit board
PAL_RUNE = " .\u16a0\u16a2\u16a6\u16b1\u16b7\u16c1\u16c7\u16d2\u16d6\u16da\u16de\u16df" # elder futhark runes
PAL_ALCHEMIC = " \u2609\u263d\u2640\u2642\u2643\u2644\u2645\u2646\u2647\u2648\u2649\u264a\u264b" # planetary/alchemical symbols
PAL_ZODIAC = " \u2648\u2649\u264a\u264b\u264c\u264d\u264e\u264f\u2650\u2651\u2652\u2653" # zodiac
PAL_ARROWS = " \u2190\u2191\u2192\u2193\u2194\u2195\u2196\u2197\u2198\u2199\u21a9\u21aa\u21bb\u27a1" # directional arrows
PAL_MUSIC = " \u266a\u266b\u266c\u2669\u266d\u266e\u266f\u25cb\u25cf" # musical notation
```
#### Script / Writing System
```python
PAL_KATA = " \u00b7\uff66\uff67\uff68\uff69\uff6a\uff6b\uff6c\uff6d\uff6e\uff6f\uff70\uff71\uff72\uff73\uff74\uff75\uff76\uff77" # katakana halfwidth (matrix rain)
PAL_GREEK = " \u03b1\u03b2\u03b3\u03b4\u03b5\u03b6\u03b7\u03b8\u03b9\u03ba\u03bb\u03bc\u03bd\u03be\u03c0\u03c1\u03c3\u03c4\u03c6\u03c8\u03c9" # Greek lowercase
PAL_CYRILLIC = " \u0430\u0431\u0432\u0433\u0434\u0435\u0436\u0437\u0438\u043a\u043b\u043c\u043d\u043e\u043f\u0440\u0441\u0442\u0443\u0444\u0445\u0446\u0447\u0448" # Cyrillic lowercase
PAL_ARABIC = " \u0627\u0628\u062a\u062b\u062c\u062d\u062e\u062f\u0630\u0631\u0632\u0633\u0634\u0635\u0636\u0637" # Arabic letters (isolated forms)
```
#### Dot / Point Progressions
```python
PAL_DOTS = " \u22c5\u2218\u2219\u25cf\u25c9\u25ce\u25c6\u2726\u2605" # dot size progression
PAL_BRAILLE = " \u2801\u2802\u2803\u2804\u2805\u2806\u2807\u2808\u2809\u280a\u280b\u280c\u280d\u280e\u280f\u2810\u2811\u2812\u2813\u2814\u2815\u2816\u2817\u2818\u2819\u281a\u281b\u281c\u281d\u281e\u281f\u283f" # braille patterns
PAL_STARS = " \u00b7\u2727\u2726\u2729\u2728\u2605\u2736\u2733\u2738" # star progression
```
#### Project-Specific (examples -- invent new ones per project)
```python
PAL_HERMES = " .\u00b7~=\u2248\u221e\u26a1\u263f\u2726\u2605\u2295\u25ca\u25c6\u25b2\u25bc\u25cf\u25a0" # mythology/tech blend
PAL_OCEAN = " ~\u2248\u2248\u2248\u223c\u2307\u2248\u224b\u224c\u2248" # water/wave characters
PAL_ORGANIC = " .\u00b0\u2218\u2022\u25e6\u25c9\u2742\u273f\u2741\u2743" # growing/botanical
PAL_MACHINE = " _\u2500\u2502\u250c\u2510\u253c\u2261\u25a0\u2588\u2593\u2592\u2591" # mechanical/industrial
```
### Creating Custom Palettes
When designing for a project, build palettes from the content's theme:
1. **Choose a visual family** (dots, blocks, symbols, script)
2. **Sort by visual weight** -- render each char at target font size, count lit pixels, sort ascending
3. **Test at target grid size** -- some chars collapse to blobs at small sizes
4. **Validate in font** -- remove chars the font can't render:
```python
def validate_palette(pal, font):
"""Remove characters the font can't render."""
valid = []
for c in pal:
if c == " ":
valid.append(c)
continue
img = Image.new("L", (20, 20), 0)
ImageDraw.Draw(img).text((0, 0), c, fill=255, font=font)
if np.array(img).max() > 0: # char actually rendered something
valid.append(c)
return "".join(valid)
```
### Mapping Values to Characters
```python
def val2char(v, mask, pal=PAL_DEFAULT):
"""Map float array (0-1) to character array using palette."""
n = len(pal)
idx = np.clip((v * n).astype(int), 0, n - 1)
out = np.full(v.shape, " ", dtype="U1")
for i, ch in enumerate(pal):
out[mask & (idx == i)] = ch
return out
```
**Nonlinear mapping** for different visual curves:
```python
def val2char_gamma(v, mask, pal, gamma=1.0):
"""Gamma-corrected palette mapping. gamma<1 = brighter, gamma>1 = darker."""
v_adj = np.power(np.clip(v, 0, 1), gamma)
return val2char(v_adj, mask, pal)
def val2char_step(v, mask, pal, thresholds):
"""Custom threshold mapping. thresholds = list of float breakpoints."""
out = np.full(v.shape, pal[0], dtype="U1")
for i, thr in enumerate(thresholds):
out[mask & (v > thr)] = pal[min(i + 1, len(pal) - 1)]
return out
```
---
## Color System
### HSV->RGB (Vectorized)
All color computation in HSV for intuitive control, converted at render time:
```python
def hsv2rgb(h, s, v):
"""Vectorized HSV->RGB. h,s,v are numpy arrays. Returns (R,G,B) uint8 arrays."""
h = h % 1.0
c = v * s; x = c * (1 - np.abs((h*6) % 2 - 1)); m = v - c
# ... 6 sector assignment ...
return (np.clip((r+m)*255, 0, 255).astype(np.uint8),
np.clip((g+m)*255, 0, 255).astype(np.uint8),
np.clip((b+m)*255, 0, 255).astype(np.uint8))
```
### Color Mapping Strategies
Don't default to a single strategy. Choose based on the visual intent:
| Strategy | Hue source | Effect | Good for |
|----------|------------|--------|----------|
| Angle-mapped | `g.angle / (2*pi)` | Rainbow around center | Radial effects, kaleidoscopes |
| Distance-mapped | `g.dist_n * 0.3` | Gradient from center | Tunnels, depth effects |
| Frequency-mapped | `f["cent"] * 0.2` | Timbral color shifting | Audio-reactive |
| Value-mapped | `val * 0.15` | Brightness-dependent hue | Fire, heat maps |
| Time-cycled | `t * rate` | Slow color rotation | Ambient, chill |
| Source-sampled | Video frame pixel colors | Preserve original color | Video-to-ASCII |
| Palette-indexed | Discrete color lookup | Flat graphic style | Retro, pixel art |
| Temperature | Blend between warm/cool | Emotional tone | Mood-driven scenes |
| Complementary | `hue` and `hue + 0.5` | High contrast | Bold, dramatic |
| Triadic | `hue`, `hue + 0.33`, `hue + 0.66` | Vibrant, balanced | Psychedelic |
| Analogous | `hue +/- 0.08` | Harmonious, subtle | Elegant, cohesive |
| Monochrome | Fixed hue, vary S and V | Restrained, focused | Noir, minimal |
### Color Palettes (Discrete RGB)
For non-HSV workflows -- direct RGB color sets for graphic/retro looks:
```python
# Named color palettes -- use for flat/graphic styles or per-character coloring
COLORS_NEON = [(255,0,102), (0,255,153), (102,0,255), (255,255,0), (0,204,255)]
COLORS_PASTEL = [(255,179,186), (255,223,186), (255,255,186), (186,255,201), (186,225,255)]
COLORS_MONO_GREEN = [(0,40,0), (0,80,0), (0,140,0), (0,200,0), (0,255,0)]
COLORS_MONO_AMBER = [(40,20,0), (80,50,0), (140,90,0), (200,140,0), (255,191,0)]
COLORS_CYBERPUNK = [(255,0,60), (0,255,200), (180,0,255), (255,200,0)]
COLORS_VAPORWAVE = [(255,113,206), (1,205,254), (185,103,255), (5,255,161)]
COLORS_EARTH = [(86,58,26), (139,90,43), (189,154,91), (222,193,136), (245,230,193)]
COLORS_ICE = [(200,230,255), (150,200,240), (100,170,230), (60,130,210), (30,80,180)]
COLORS_BLOOD = [(80,0,0), (140,10,10), (200,20,20), (255,50,30), (255,100,80)]
COLORS_FOREST = [(10,30,10), (20,60,15), (30,100,20), (50,150,30), (80,200,50)]
def rgb_palette_map(val, mask, palette):
"""Map float array (0-1) to RGB colors from a discrete palette."""
n = len(palette)
idx = np.clip((val * n).astype(int), 0, n - 1)
R = np.zeros(val.shape, dtype=np.uint8)
G = np.zeros(val.shape, dtype=np.uint8)
B = np.zeros(val.shape, dtype=np.uint8)
for i, (r, g, b) in enumerate(palette):
m = mask & (idx == i)
R[m] = r; G[m] = g; B[m] = b
return R, G, B
```
### Compositing Helpers
```python
def mkc(R, G, B, rows, cols):
"""Pack 3 uint8 arrays into (rows, cols, 3) color array."""
o = np.zeros((rows, cols, 3), dtype=np.uint8)
o[:,:,0] = R; o[:,:,1] = G; o[:,:,2] = B
return o
def layer_over(base_ch, base_co, top_ch, top_co):
"""Composite top layer onto base. Non-space chars overwrite."""
m = top_ch != " "
base_ch[m] = top_ch[m]; base_co[m] = top_co[m]
return base_ch, base_co
def layer_blend(base_co, top_co, alpha):
"""Alpha-blend top color layer onto base. alpha is float array (0-1) or scalar."""
if isinstance(alpha, (int, float)):
alpha = np.full(base_co.shape[:2], alpha, dtype=np.float32)
a = alpha[:,:,None]
return np.clip(base_co * (1 - a) + top_co * a, 0, 255).astype(np.uint8)
def stamp(ch, co, text, row, col, color=(255,255,255)):
"""Write text string at position."""
for i, c in enumerate(text):
cc = col + i
if 0 <= row < ch.shape[0] and 0 <= cc < ch.shape[1]:
ch[row, cc] = c; co[row, cc] = color
```
---
## Section System
Map time ranges to effect functions + shader configs + grid sizes:
```python
SECTIONS = [
(0.0, "void"), (3.94, "starfield"), (21.0, "matrix"),
(46.0, "drop"), (130.0, "glitch"), (187.0, "outro"),
]
FX_DISPATCH = {"void": fx_void, "starfield": fx_starfield, ...}
SECTION_FX = {"void": {"vignette": 0.3, "bloom": 170}, ...}
SECTION_GRID = {"void": "md", "starfield": "sm", "drop": "lg", ...}
SECTION_MIRROR = {"drop": "h", "bass_rings": "quad"}
def get_section(t):
sec = SECTIONS[0][1]
for ts, name in SECTIONS:
if t >= ts: sec = name
return sec
```
---
## Parallel Encoding
Split frames across N workers. Each pipes raw RGB to its own ffmpeg subprocess:
```python
def render_batch(batch_id, frame_start, frame_end, features, seg_path):
r = Renderer()
cmd = ["ffmpeg", "-y", "-f", "rawvideo", "-pix_fmt", "rgb24",
"-s", f"{VW}x{VH}", "-r", str(FPS), "-i", "pipe:0",
"-c:v", "libx264", "-preset", "fast", "-crf", "18",
"-pix_fmt", "yuv420p", seg_path]
# CRITICAL: stderr to file, not pipe
stderr_fh = open(os.path.join(workdir, f"err_{batch_id:02d}.log"), "w")
pipe = subprocess.Popen(cmd, stdin=subprocess.PIPE,
stdout=subprocess.DEVNULL, stderr=stderr_fh)
for fi in range(frame_start, frame_end):
t = fi / FPS
sec = get_section(t)
f = {k: float(features[k][fi]) for k in features}
ch, co = FX_DISPATCH[sec](r, f, t)
canvas = r.render(ch, co)
canvas = apply_mirror(canvas, sec, f)
canvas = apply_shaders(canvas, sec, f, t)
pipe.stdin.write(canvas.tobytes())
pipe.stdin.close()
pipe.wait()
stderr_fh.close()
```
Concatenate segments + mux audio:
```python
# Write concat file
with open(concat_path, "w") as cf:
for seg in segments:
cf.write(f"file '{seg}'\n")
subprocess.run(["ffmpeg", "-y", "-f", "concat", "-safe", "0", "-i", concat_path,
"-i", audio_path, "-c:v", "copy", "-c:a", "aac", "-b:a", "192k",
"-shortest", output_path])
```
## Effect Function Contract
### v2 Protocol (Current)
Every scene function: `(renderer, features_dict, time_float, state_dict) -> canvas_uint8`
```python
def fx_example(r, f, t, S):
"""Scene function returns a full pixel canvas (uint8 H,W,3).
Scenes have full control over multi-grid rendering and pixel-level composition.
"""
# Render multiple layers at different grid densities
canvas_a = _render_vf(r, "md", vf_plasma, hf_angle(0.0), PAL_DENSE, f, t, S)
canvas_b = _render_vf(r, "sm", vf_vortex, hf_time_cycle(0.1), PAL_RUNE, f, t, S)
# Pixel-level blend
result = blend_canvas(canvas_a, canvas_b, "screen", 0.8)
return result
```
See `references/scenes.md` for the full scene protocol, the Renderer class, `_render_vf()` helper, and complete scene examples.
See `references/composition.md` for blend modes, tone mapping, feedback buffers, and multi-grid composition.
### v1 Protocol (Legacy)
Simple scenes that use a single grid can still return `(chars, colors)` and let the caller handle rendering, but the v2 canvas protocol is preferred for all new code.
```python
def fx_simple(r, f, t, S):
g = r.get_grid("md")
val = np.sin(g.dist * 0.1 - t * 3) * f.get("bass", 0.3) * 2
val = np.clip(val, 0, 1); mask = val > 0.03
ch = val2char(val, mask, PAL_DEFAULT)
R, G, B = hsv2rgb(np.full_like(val, 0.6), np.full_like(val, 0.7), val)
co = mkc(R, G, B, g.rows, g.cols)
return g.render(ch, co) # returns canvas directly
```
### Persistent State
Effects that need state across frames (particles, rain columns) use the `S` dict parameter (which is `r.S` — same object, but passed explicitly for clarity):
```python
def fx_with_state(r, f, t, S):
if "particles" not in S:
S["particles"] = initialize_particles()
update_particles(S["particles"])
# ...
```
State persists across frames within a single scene/clip. Each worker process (and each scene) gets its own independent state.
### Helper Functions
```python
def hsv2rgb_scalar(h, s, v):
"""Single-value HSV to RGB. Returns (R, G, B) tuple of ints 0-255."""
h = h % 1.0
c = v * s; x = c * (1 - abs((h * 6) % 2 - 1)); m = v - c
if h * 6 < 1: r, g, b = c, x, 0
elif h * 6 < 2: r, g, b = x, c, 0
elif h * 6 < 3: r, g, b = 0, c, x
elif h * 6 < 4: r, g, b = 0, x, c
elif h * 6 < 5: r, g, b = x, 0, c
else: r, g, b = c, 0, x
return (int((r+m)*255), int((g+m)*255), int((b+m)*255))
def log(msg):
"""Print timestamped log message."""
print(msg, flush=True)
```

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# Composition & Brightness Reference
The composable system is the core of visual complexity. It operates at three levels: pixel-level blend modes, multi-grid composition, and adaptive brightness management. This document covers all three.
## Pixel-Level Blend Modes
### The `blend_canvas()` Function
All blending operates on full pixel canvases (`uint8 H,W,3`). Internally converts to float32 [0,1] for precision, blends, lerps by opacity, converts back.
```python
def blend_canvas(base, top, mode="normal", opacity=1.0):
af = base.astype(np.float32) / 255.0
bf = top.astype(np.float32) / 255.0
fn = BLEND_MODES.get(mode, BLEND_MODES["normal"])
result = fn(af, bf)
if opacity < 1.0:
result = af * (1 - opacity) + result * opacity
return np.clip(result * 255, 0, 255).astype(np.uint8)
```
### 20 Blend Modes
```python
BLEND_MODES = {
# Basic arithmetic
"normal": lambda a, b: b,
"add": lambda a, b: np.clip(a + b, 0, 1),
"subtract": lambda a, b: np.clip(a - b, 0, 1),
"multiply": lambda a, b: a * b,
"screen": lambda a, b: 1 - (1 - a) * (1 - b),
# Contrast
"overlay": lambda a, b: np.where(a < 0.5, 2*a*b, 1 - 2*(1-a)*(1-b)),
"softlight": lambda a, b: (1 - 2*b)*a*a + 2*b*a,
"hardlight": lambda a, b: np.where(b < 0.5, 2*a*b, 1 - 2*(1-a)*(1-b)),
# Difference
"difference": lambda a, b: np.abs(a - b),
"exclusion": lambda a, b: a + b - 2*a*b,
# Dodge / burn
"colordodge": lambda a, b: np.clip(a / (1 - b + 1e-6), 0, 1),
"colorburn": lambda a, b: np.clip(1 - (1 - a) / (b + 1e-6), 0, 1),
# Light
"linearlight": lambda a, b: np.clip(a + 2*b - 1, 0, 1),
"vividlight": lambda a, b: np.where(b < 0.5,
np.clip(1 - (1-a)/(2*b + 1e-6), 0, 1),
np.clip(a / (2*(1-b) + 1e-6), 0, 1)),
"pin_light": lambda a, b: np.where(b < 0.5,
np.minimum(a, 2*b), np.maximum(a, 2*b - 1)),
"hard_mix": lambda a, b: np.where(a + b >= 1.0, 1.0, 0.0),
# Compare
"lighten": lambda a, b: np.maximum(a, b),
"darken": lambda a, b: np.minimum(a, b),
# Grain
"grain_extract": lambda a, b: np.clip(a - b + 0.5, 0, 1),
"grain_merge": lambda a, b: np.clip(a + b - 0.5, 0, 1),
}
```
### Blend Mode Selection Guide
**Modes that brighten** (safe for dark inputs):
- `screen` — always brightens. Two 50% gray layers screen to 75%. The go-to safe blend.
- `add` — simple addition, clips at white. Good for sparkles, glows, particle overlays.
- `colordodge` — extreme brightening at overlap zones. Can blow out. Use low opacity (0.3-0.5).
- `linearlight` — aggressive brightening. Similar to add but with offset.
**Modes that darken** (avoid with dark inputs):
- `multiply` — darkens everything. Only use when both layers are already bright.
- `overlay` — darkens when base < 0.5, brightens when base > 0.5. Crushes dark inputs: `2 * 0.12 * 0.12 = 0.03`. Use `screen` instead for dark material.
- `colorburn` — extreme darkening at overlap zones.
**Modes that create contrast**:
- `softlight` — gentle contrast. Good for subtle texture overlay.
- `hardlight` — strong contrast. Like overlay but keyed on the top layer.
- `vividlight` — very aggressive contrast. Use sparingly.
**Modes that create color effects**:
- `difference` — XOR-like patterns. Two identical layers difference to black; offset layers create wild colors. Great for psychedelic looks.
- `exclusion` — softer version of difference. Creates complementary color patterns.
- `hard_mix` — posterizes to pure black/white/saturated color at intersections.
**Modes for texture blending**:
- `grain_extract` / `grain_merge` — extract a texture from one layer, apply it to another.
### Multi-Layer Chaining
```python
# Pattern: render layers -> blend sequentially
canvas_a = _render_vf(r, "md", vf_plasma, hf_angle(0.0), PAL_DENSE, f, t, S)
canvas_b = _render_vf(r, "sm", vf_vortex, hf_time_cycle(0.1), PAL_RUNE, f, t, S)
canvas_c = _render_vf(r, "lg", vf_rings, hf_distance(), PAL_BLOCKS, f, t, S)
result = blend_canvas(canvas_a, canvas_b, "screen", 0.8)
result = blend_canvas(result, canvas_c, "difference", 0.6)
```
Order matters: `screen(A, B)` is commutative, but `difference(screen(A,B), C)` differs from `difference(A, screen(B,C))`.
---
## Multi-Grid Composition
This is the core visual technique. Rendering the same conceptual scene at different grid densities (character sizes) creates natural texture interference, because characters at different scales overlap at different spatial frequencies.
### Why It Works
- `sm` grid (10pt font): 320x83 characters. Fine detail, dense texture.
- `md` grid (16pt): 192x56 characters. Medium density.
- `lg` grid (20pt): 160x45 characters. Coarse, chunky characters.
When you render a plasma field on `sm` and a vortex on `lg`, then screen-blend them, the fine plasma texture shows through the gaps in the coarse vortex characters. The result has more visual complexity than either layer alone.
### The `_render_vf()` Helper
This is the workhorse function. It takes a value field + hue field + palette + grid, renders to a complete pixel canvas:
```python
def _render_vf(r, grid_key, val_fn, hue_fn, pal, f, t, S, sat=0.8, threshold=0.03):
"""Render a value field + hue field to a pixel canvas via a named grid.
Args:
r: Renderer instance (has .get_grid())
grid_key: "xs", "sm", "md", "lg", "xl", "xxl"
val_fn: (g, f, t, S) -> float32 [0,1] array (rows, cols)
hue_fn: callable (g, f, t, S) -> float32 hue array, OR float scalar
pal: character palette string
f: feature dict
t: time in seconds
S: persistent state dict
sat: HSV saturation (0-1)
threshold: minimum value to render (below = space)
Returns:
uint8 array (VH, VW, 3) — full pixel canvas
"""
g = r.get_grid(grid_key)
val = np.clip(val_fn(g, f, t, S), 0, 1)
mask = val > threshold
ch = val2char(val, mask, pal)
# Hue: either a callable or a fixed float
if callable(hue_fn):
h = hue_fn(g, f, t, S) % 1.0
else:
h = np.full((g.rows, g.cols), float(hue_fn), dtype=np.float32)
# CRITICAL: broadcast to full shape and copy (see Troubleshooting)
h = np.broadcast_to(h, (g.rows, g.cols)).copy()
R, G, B = hsv2rgb(h, np.full_like(val, sat), val)
co = mkc(R, G, B, g.rows, g.cols)
return g.render(ch, co)
```
### Grid Combination Strategies
| Combination | Effect | Good For |
|-------------|--------|----------|
| `sm` + `lg` | Maximum contrast between fine detail and chunky blocks | Bold, graphic looks |
| `sm` + `md` | Subtle texture layering, similar scales | Organic, flowing looks |
| `md` + `lg` + `xs` | Three-scale interference, maximum complexity | Psychedelic, dense |
| `sm` + `sm` (different effects) | Same scale, pattern interference only | Moire, interference |
### Complete Multi-Grid Scene Example
```python
def fx_psychedelic(r, f, t, S):
"""Three-layer multi-grid scene with beat-reactive kaleidoscope."""
# Layer A: plasma on medium grid with rainbow hue
canvas_a = _render_vf(r, "md",
lambda g, f, t, S: vf_plasma(g, f, t, S) * 1.3,
hf_angle(0.0), PAL_DENSE, f, t, S, sat=0.8)
# Layer B: vortex on small grid with cycling hue
canvas_b = _render_vf(r, "sm",
lambda g, f, t, S: vf_vortex(g, f, t, S, twist=5.0) * 1.2,
hf_time_cycle(0.1), PAL_RUNE, f, t, S, sat=0.7)
# Layer C: rings on large grid with distance hue
canvas_c = _render_vf(r, "lg",
lambda g, f, t, S: vf_rings(g, f, t, S, n_base=8, spacing_base=3) * 1.4,
hf_distance(0.3, 0.02), PAL_BLOCKS, f, t, S, sat=0.9)
# Blend: A screened with B, then difference with C
result = blend_canvas(canvas_a, canvas_b, "screen", 0.8)
result = blend_canvas(result, canvas_c, "difference", 0.6)
# Beat-triggered kaleidoscope
if f.get("bdecay", 0) > 0.3:
result = sh_kaleidoscope(result.copy(), folds=6)
return result
```
---
## Adaptive Tone Mapping
### The Brightness Problem
ASCII characters are small bright dots on a black background. Most pixels in any frame are background (black). This means:
- Mean frame brightness is inherently low (often 5-30 out of 255)
- Different effect combinations produce wildly different brightness levels
- A spiral scene might be 50 mean, while a fire scene is 9 mean
- Linear multipliers (e.g., `canvas * 2.0`) either leave dark scenes dark or blow out bright scenes
### The `tonemap()` Function
Replaces linear brightness multipliers with adaptive per-frame normalization + gamma correction:
```python
def tonemap(canvas, target_mean=90, gamma=0.75, black_point=2, white_point=253):
"""Adaptive tone-mapping: normalizes + gamma-corrects so no frame is
fully dark or washed out.
1. Compute 1st and 99.5th percentile (ignores outlier pixels)
2. Stretch that range to [0, 1]
3. Apply gamma curve (< 1 lifts shadows, > 1 darkens)
4. Rescale to [black_point, white_point]
"""
f = canvas.astype(np.float32)
lo = np.percentile(f, 1)
hi = np.percentile(f, 99.5)
if hi - lo < 10:
hi = max(hi, lo + 10) # near-uniform frame fallback
f = np.clip((f - lo) / (hi - lo), 0.0, 1.0)
f = np.power(f, gamma)
f = f * (white_point - black_point) + black_point
return np.clip(f, 0, 255).astype(np.uint8)
```
### Why Gamma, Not Linear
Linear multiplier `* 2.0`:
```
input 10 -> output 20 (still dark)
input 100 -> output 200 (ok)
input 200 -> output 255 (clipped, lost detail)
```
Gamma 0.75 after normalization:
```
input 0.04 -> output 0.08 (lifted from invisible to visible)
input 0.39 -> output 0.50 (moderate lift)
input 0.78 -> output 0.84 (gentle lift, no clipping)
```
Gamma < 1 compresses the highlights and expands the shadows. This is exactly what we need: lift dark ASCII content into visibility without blowing out the bright parts.
### Pipeline Ordering
The pipeline in `render_clip()` is:
```
scene_fn(r, f, t, S) -> canvas
|
tonemap(canvas, gamma=scene_gamma)
|
FeedbackBuffer.apply(canvas, ...)
|
ShaderChain.apply(canvas, f=f, t=t)
|
ffmpeg pipe
```
Tonemap runs BEFORE feedback and shaders. This means:
- Feedback operates on normalized data (consistent behavior regardless of scene brightness)
- Shaders like solarize, posterize, contrast operate on properly-ranged data
- The brightness shader in the chain is no longer needed (tonemap handles it)
### Per-Scene Gamma Tuning
Default gamma is 0.75. Scenes that apply destructive post-processing need more aggressive lift because the destruction happens after tonemap:
| Scene Type | Recommended Gamma | Why |
|------------|-------------------|-----|
| Standard effects | 0.75 | Default, works for most scenes |
| Solarize post-process | 0.50-0.60 | Solarize inverts bright pixels, reducing overall brightness |
| Posterize post-process | 0.50-0.55 | Posterize quantizes, often crushing mid-values to black |
| Heavy difference blending | 0.60-0.70 | Difference mode creates many near-zero pixels |
| Already bright scenes | 0.85-1.0 | Don't over-boost scenes that are naturally bright |
Configure via the scene table:
```python
SCENES = [
{"start": 9.17, "end": 11.25, "name": "fire", "gamma": 0.55,
"fx": fx_fire, "shaders": [("solarize", {"threshold": 200}), ...]},
{"start": 25.96, "end": 27.29, "name": "diamond", "gamma": 0.5,
"fx": fx_diamond, "shaders": [("bloom", {"thr": 90}), ...]},
]
```
### Brightness Verification
After rendering, spot-check frame brightness:
```python
# In test-frame mode
canvas = scene["fx"](r, feat, t, r.S)
canvas = tonemap(canvas, gamma=scene.get("gamma", 0.75))
chain = ShaderChain()
for sn, kw in scene.get("shaders", []):
chain.add(sn, **kw)
canvas = chain.apply(canvas, f=feat, t=t)
print(f"Mean brightness: {canvas.astype(float).mean():.1f}, max: {canvas.max()}")
```
Target ranges after tonemap + shaders:
- Quiet/ambient scenes: mean 30-60
- Active scenes: mean 40-100
- Climax/peak scenes: mean 60-150
- If mean < 20: gamma is too high or a shader is destroying brightness
- If mean > 180: gamma is too low or add is stacking too much
---
## FeedbackBuffer Spatial Transforms
The feedback buffer stores the previous frame and blends it into the current frame with decay. Spatial transforms applied to the buffer before blending create the illusion of motion in the feedback trail.
### Implementation
```python
class FeedbackBuffer:
def __init__(self):
self.buf = None
def apply(self, canvas, decay=0.85, blend="screen", opacity=0.5,
transform=None, transform_amt=0.02, hue_shift=0.0):
if self.buf is None:
self.buf = canvas.astype(np.float32) / 255.0
return canvas
# Decay old buffer
self.buf *= decay
# Spatial transform
if transform:
self.buf = self._transform(self.buf, transform, transform_amt)
# Hue shift the feedback for rainbow trails
if hue_shift > 0:
self.buf = self._hue_shift(self.buf, hue_shift)
# Blend feedback into current frame
result = blend_canvas(canvas,
np.clip(self.buf * 255, 0, 255).astype(np.uint8),
blend, opacity)
# Update buffer with current frame
self.buf = result.astype(np.float32) / 255.0
return result
def _transform(self, buf, transform, amt):
h, w = buf.shape[:2]
if transform == "zoom":
# Zoom in: sample from slightly inside (creates expanding tunnel)
m = int(h * amt); n = int(w * amt)
if m > 0 and n > 0:
cropped = buf[m:-m or None, n:-n or None]
# Resize back to full (nearest-neighbor for speed)
buf = np.array(Image.fromarray(
np.clip(cropped * 255, 0, 255).astype(np.uint8)
).resize((w, h), Image.NEAREST)).astype(np.float32) / 255.0
elif transform == "shrink":
# Zoom out: pad edges, shrink center
m = int(h * amt); n = int(w * amt)
small = np.array(Image.fromarray(
np.clip(buf * 255, 0, 255).astype(np.uint8)
).resize((w - 2*n, h - 2*m), Image.NEAREST))
new = np.zeros((h, w, 3), dtype=np.uint8)
new[m:m+small.shape[0], n:n+small.shape[1]] = small
buf = new.astype(np.float32) / 255.0
elif transform == "rotate_cw":
# Small clockwise rotation via affine
angle = amt * 10 # amt=0.005 -> 0.05 degrees per frame
cy, cx = h / 2, w / 2
Y = np.arange(h, dtype=np.float32)[:, None]
X = np.arange(w, dtype=np.float32)[None, :]
cos_a, sin_a = np.cos(angle), np.sin(angle)
sx = (X - cx) * cos_a + (Y - cy) * sin_a + cx
sy = -(X - cx) * sin_a + (Y - cy) * cos_a + cy
sx = np.clip(sx.astype(int), 0, w - 1)
sy = np.clip(sy.astype(int), 0, h - 1)
buf = buf[sy, sx]
elif transform == "rotate_ccw":
angle = -amt * 10
cy, cx = h / 2, w / 2
Y = np.arange(h, dtype=np.float32)[:, None]
X = np.arange(w, dtype=np.float32)[None, :]
cos_a, sin_a = np.cos(angle), np.sin(angle)
sx = (X - cx) * cos_a + (Y - cy) * sin_a + cx
sy = -(X - cx) * sin_a + (Y - cy) * cos_a + cy
sx = np.clip(sx.astype(int), 0, w - 1)
sy = np.clip(sy.astype(int), 0, h - 1)
buf = buf[sy, sx]
elif transform == "shift_up":
pixels = max(1, int(h * amt))
buf = np.roll(buf, -pixels, axis=0)
buf[-pixels:] = 0 # black fill at bottom
elif transform == "shift_down":
pixels = max(1, int(h * amt))
buf = np.roll(buf, pixels, axis=0)
buf[:pixels] = 0
elif transform == "mirror_h":
buf = buf[:, ::-1]
return buf
def _hue_shift(self, buf, amount):
"""Rotate hues of the feedback buffer. Operates on float32 [0,1]."""
rgb = np.clip(buf * 255, 0, 255).astype(np.uint8)
hsv = np.zeros_like(buf)
# Simple approximate RGB->HSV->shift->RGB
r, g, b = buf[:,:,0], buf[:,:,1], buf[:,:,2]
mx = np.maximum(np.maximum(r, g), b)
mn = np.minimum(np.minimum(r, g), b)
delta = mx - mn + 1e-10
# Hue
h = np.where(mx == r, ((g - b) / delta) % 6,
np.where(mx == g, (b - r) / delta + 2, (r - g) / delta + 4))
h = (h / 6 + amount) % 1.0
# Reconstruct with shifted hue (simplified)
s = delta / (mx + 1e-10)
v = mx
c = v * s; x = c * (1 - np.abs((h * 6) % 2 - 1)); m = v - c
ro = np.zeros_like(h); go = np.zeros_like(h); bo = np.zeros_like(h)
for lo, hi, rv, gv, bv in [(0,1,c,x,0),(1,2,x,c,0),(2,3,0,c,x),
(3,4,0,x,c),(4,5,x,0,c),(5,6,c,0,x)]:
mask = ((h*6) >= lo) & ((h*6) < hi)
ro[mask] = rv[mask] if not isinstance(rv, (int,float)) else rv
go[mask] = gv[mask] if not isinstance(gv, (int,float)) else gv
bo[mask] = bv[mask] if not isinstance(bv, (int,float)) else bv
return np.stack([ro+m, go+m, bo+m], axis=2)
```
### Feedback Presets
| Preset | Config | Visual Effect |
|--------|--------|---------------|
| Infinite zoom tunnel | `decay=0.8, blend="screen", transform="zoom", transform_amt=0.015` | Expanding ring patterns |
| Rainbow trails | `decay=0.7, blend="screen", transform="zoom", transform_amt=0.01, hue_shift=0.02` | Psychedelic color trails |
| Ghostly echo | `decay=0.9, blend="add", opacity=0.15, transform="shift_up", transform_amt=0.01` | Faint upward smearing |
| Kaleidoscopic recursion | `decay=0.75, blend="screen", transform="rotate_cw", transform_amt=0.005, hue_shift=0.01` | Rotating mandala feedback |
| Color evolution | `decay=0.8, blend="difference", opacity=0.4, hue_shift=0.03` | Frame-to-frame color XOR |
| Rising heat haze | `decay=0.5, blend="add", opacity=0.2, transform="shift_up", transform_amt=0.02` | Hot air shimmer |
---
## PixelBlendStack
Higher-level wrapper for multi-layer compositing:
```python
class PixelBlendStack:
def __init__(self):
self.layers = []
def add(self, canvas, mode="normal", opacity=1.0):
self.layers.append((canvas, mode, opacity))
return self
def composite(self):
if not self.layers:
return np.zeros((VH, VW, 3), dtype=np.uint8)
result = self.layers[0][0]
for canvas, mode, opacity in self.layers[1:]:
result = blend_canvas(result, canvas, mode, opacity)
return result
```

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# Effect Catalog
Effect building blocks that produce visual patterns. In v2, these are used **inside scene functions** that return a pixel canvas directly. The building blocks below operate on grid coordinate arrays and produce `(chars, colors)` or value/hue fields that the scene function renders to canvas via `_render_vf()`. See `composition.md` for the v2 rendering pattern and `scenes.md` for scene function examples.
## Design Philosophy
Effects are the creative core. Don't copy these verbatim for every project -- use them as **building blocks** and **combine, modify, and invent** new ones. Every project should feel distinct.
Key principles:
- **Layer multiple effects** rather than using a single monolithic function
- **Parameterize everything** -- hue, speed, density, amplitude should all be arguments
- **React to features** -- audio/video features should modulate at least 2-3 parameters per effect
- **Vary per section** -- never use the same effect config for the entire video
- **Invent project-specific effects** -- the catalog below is a starting vocabulary, not a fixed set
---
## Background Fills
Every effect should start with a background. Never leave flat black.
### Animated Sine Field (General Purpose)
```python
def bg_sinefield(g, f, t, hue=0.6, bri=0.5, pal=PAL_DEFAULT,
freq=(0.13, 0.17, 0.07, 0.09), speed=(0.5, -0.4, -0.3, 0.2)):
"""Layered sine field. Adjust freq/speed tuples for different textures."""
v1 = np.sin(g.cc*freq[0] + t*speed[0]) * np.sin(g.rr*freq[1] - t*speed[1]) * 0.5 + 0.5
v2 = np.sin(g.cc*freq[2] - t*speed[2] + g.rr*freq[3]) * 0.4 + 0.5
v3 = np.sin(g.dist_n*5 + t*0.2) * 0.3 + 0.4
v4 = np.cos(g.angle*3 - t*0.6) * 0.15 + 0.5
val = np.clip((v1*0.3 + v2*0.25 + v3*0.25 + v4*0.2) * bri * (0.6 + f["rms"]*0.6), 0.06, 1)
mask = val > 0.03
ch = val2char(val, mask, pal)
h = np.full_like(val, hue) + f.get("cent", 0.5)*0.1 + val*0.08
R, G, B = hsv2rgb(h, np.clip(0.35+f.get("flat",0.4)*0.4, 0, 1) * np.ones_like(val), val)
return ch, mkc(R, G, B, g.rows, g.cols)
```
### Video-Source Background
```python
def bg_video(g, frame_rgb, pal=PAL_DEFAULT, brightness=0.5):
small = np.array(Image.fromarray(frame_rgb).resize((g.cols, g.rows)))
lum = np.mean(small, axis=2) / 255.0 * brightness
mask = lum > 0.02
ch = val2char(lum, mask, pal)
co = np.clip(small * np.clip(lum[:,:,None]*1.5+0.3, 0.3, 1), 0, 255).astype(np.uint8)
return ch, co
```
### Noise / Static Field
```python
def bg_noise(g, f, t, pal=PAL_BLOCKS, density=0.3, hue_drift=0.02):
val = np.random.random((g.rows, g.cols)).astype(np.float32) * density * (0.5 + f["rms"]*0.5)
val = np.clip(val, 0, 1); mask = val > 0.02
ch = val2char(val, mask, pal)
R, G, B = hsv2rgb(np.full_like(val, t*hue_drift % 1), np.full_like(val, 0.3), val)
return ch, mkc(R, G, B, g.rows, g.cols)
```
### Perlin-Like Smooth Noise
```python
def bg_smooth_noise(g, f, t, hue=0.5, bri=0.5, pal=PAL_DOTS, octaves=3):
"""Layered sine approximation of Perlin noise. Cheap, smooth, organic."""
val = np.zeros((g.rows, g.cols), dtype=np.float32)
for i in range(octaves):
freq = 0.05 * (2 ** i)
amp = 0.5 / (i + 1)
phase = t * (0.3 + i * 0.2)
val += np.sin(g.cc * freq + phase) * np.cos(g.rr * freq * 0.7 - phase * 0.5) * amp
val = np.clip(val * 0.5 + 0.5, 0, 1) * bri
mask = val > 0.03
ch = val2char(val, mask, pal)
h = np.full_like(val, hue) + val * 0.1
R, G, B = hsv2rgb(h, np.full_like(val, 0.5), val)
return ch, mkc(R, G, B, g.rows, g.cols)
```
### Cellular / Voronoi Approximation
```python
def bg_cellular(g, f, t, n_centers=12, hue=0.5, bri=0.6, pal=PAL_BLOCKS):
"""Voronoi-like cells using distance to nearest of N moving centers."""
rng = np.random.RandomState(42) # deterministic centers
cx = (rng.rand(n_centers) * g.cols).astype(np.float32)
cy = (rng.rand(n_centers) * g.rows).astype(np.float32)
# Animate centers
cx_t = cx + np.sin(t * 0.5 + np.arange(n_centers) * 0.7) * 5
cy_t = cy + np.cos(t * 0.4 + np.arange(n_centers) * 0.9) * 3
# Min distance to any center
min_d = np.full((g.rows, g.cols), 999.0, dtype=np.float32)
for i in range(n_centers):
d = np.sqrt((g.cc - cx_t[i])**2 + (g.rr - cy_t[i])**2)
min_d = np.minimum(min_d, d)
val = np.clip(1.0 - min_d / (g.cols * 0.3), 0, 1) * bri
# Cell edges (where distance is near-equal between two centers)
# ... second-nearest trick for edge highlighting
mask = val > 0.03
ch = val2char(val, mask, pal)
R, G, B = hsv2rgb(np.full_like(val, hue) + min_d * 0.005, np.full_like(val, 0.5), val)
return ch, mkc(R, G, B, g.rows, g.cols)
```
---
## Radial Effects
### Concentric Rings
Bass/sub-driven pulsing rings from center. Scale ring count and thickness with bass energy.
```python
def eff_rings(g, f, t, hue=0.5, n_base=6, pal=PAL_DEFAULT):
n_rings = int(n_base + f["sub_r"] * 25 + f["bass"] * 10)
spacing = 2 + f["bass_r"] * 7 + f["rms"] * 3
ring_cv = np.zeros((g.rows, g.cols), dtype=np.float32)
for ri in range(n_rings):
rad = (ri+1) * spacing + f["bdecay"] * 15
wobble = f["mid_r"]*5*np.sin(g.angle*3 + t*4) + f["hi_r"]*3*np.sin(g.angle*7 - t*6)
rd = np.abs(g.dist - rad - wobble)
th = 1 + f["sub"] * 3
ring_cv = np.maximum(ring_cv, np.clip((1 - rd/th) * (0.4 + f["bass"]*0.8), 0, 1))
# Color by angle + distance for rainbow rings
h = g.angle/(2*np.pi) + g.dist*0.005 + f["sub_r"]*0.2
return ring_cv, h
```
### Radial Rays
```python
def eff_rays(g, f, t, n_base=8, hue=0.5):
n_rays = int(n_base + f["hi_r"] * 25)
ray = np.clip(np.cos(g.angle*n_rays + t*3) * f["bdecay"]*0.6 * (1-g.dist_n), 0, 0.7)
return ray
```
### Spiral Arms (Logarithmic)
```python
def eff_spiral(g, f, t, n_arms=3, tightness=2.5, hue=0.5):
arm_cv = np.zeros((g.rows, g.cols), dtype=np.float32)
for ai in range(n_arms):
offset = ai * 2*np.pi / n_arms
log_r = np.log(g.dist + 1) * tightness
arm_phase = g.angle + offset - log_r + t * 0.8
arm_val = np.clip(np.cos(arm_phase * n_arms) * 0.6 + 0.2, 0, 1)
arm_val *= (0.4 + f["rms"]*0.6) * np.clip(1 - g.dist_n*0.5, 0.2, 1)
arm_cv = np.maximum(arm_cv, arm_val)
return arm_cv
```
### Center Glow / Pulse
```python
def eff_glow(g, f, t, intensity=0.6, spread=2.0):
return np.clip(intensity * np.exp(-g.dist_n * spread) * (0.5 + f["rms"]*2 + np.sin(t*1.2)*0.2), 0, 0.9)
```
### Tunnel / Depth
```python
def eff_tunnel(g, f, t, speed=3.0, complexity=6):
tunnel_d = 1.0 / (g.dist_n + 0.1)
v1 = np.sin(tunnel_d*2 - t*speed) * 0.45 + 0.55
v2 = np.sin(g.angle*complexity + tunnel_d*1.5 - t*2) * 0.35 + 0.55
return v1 * 0.5 + v2 * 0.5
```
### Vortex (Rotating Distortion)
```python
def eff_vortex(g, f, t, twist=3.0, pulse=True):
"""Twisting radial pattern -- distance modulates angle."""
twisted = g.angle + g.dist_n * twist * np.sin(t * 0.5)
val = np.sin(twisted * 4 - t * 2) * 0.5 + 0.5
if pulse:
val *= 0.5 + f.get("bass", 0.3) * 0.8
return np.clip(val, 0, 1)
```
---
## Wave Effects
### Multi-Band Frequency Waves
Each frequency band draws its own wave at different spatial/temporal frequencies:
```python
def eff_freq_waves(g, f, t, bands=None):
if bands is None:
bands = [("sub",0.06,1.2,0.0), ("bass",0.10,2.0,0.08), ("lomid",0.15,3.0,0.16),
("mid",0.22,4.5,0.25), ("himid",0.32,6.5,0.4), ("hi",0.45,8.5,0.55)]
mid = g.rows / 2.0
composite = np.zeros((g.rows, g.cols), dtype=np.float32)
for band_key, sf, tf, hue_base in bands:
amp = f.get(band_key, 0.3) * g.rows * 0.4
y_wave = mid - np.sin(g.cc*sf + t*tf) * amp
y_wave += np.sin(g.cc*sf*2.3 + t*tf*1.7) * amp * 0.2 # harmonic
dist = np.abs(g.rr - y_wave)
thickness = 2 + f.get(band_key, 0.3) * 5
intensity = np.clip((1 - dist/thickness) * f.get(band_key, 0.3) * 1.5, 0, 1)
composite = np.maximum(composite, intensity)
return composite
```
### Interference Pattern
6-8 overlapping sine waves creating moire-like patterns:
```python
def eff_interference(g, f, t, n_waves=5):
"""Parametric interference -- vary n_waves for complexity."""
# Each wave has different orientation, frequency, and feature driver
drivers = ["mid_r", "himid_r", "bass_r", "lomid_r", "hi_r"]
vals = np.zeros((g.rows, g.cols), dtype=np.float32)
for i in range(min(n_waves, len(drivers))):
angle = i * np.pi / n_waves # spread orientations
freq = 0.06 + i * 0.03
sp = 0.5 + i * 0.3
proj = g.cc * np.cos(angle) + g.rr * np.sin(angle)
vals += np.sin(proj * freq + t * sp) * f.get(drivers[i], 0.3) * 2.5
return np.clip(vals * 0.12 + 0.45, 0.1, 1)
```
### Aurora / Horizontal Bands
```python
def eff_aurora(g, f, t, hue=0.4, n_bands=3):
val = np.zeros((g.rows, g.cols), dtype=np.float32)
for i in range(n_bands):
freq_r = 0.08 + i * 0.04
freq_c = 0.012 + i * 0.008
sp_r = 0.7 + i * 0.3
sp_c = 0.18 + i * 0.12
val += np.sin(g.rr*freq_r + t*sp_r) * np.sin(g.cc*freq_c + t*sp_c) * (0.6 / n_bands)
return np.clip(val * (f.get("lomid_r", 0.3)*3 + 0.2), 0, 0.7)
```
### Ripple (Point-Source Waves)
```python
def eff_ripple(g, f, t, sources=None, freq=0.3, damping=0.02):
"""Concentric ripples from point sources. Sources = [(row_frac, col_frac), ...]"""
if sources is None:
sources = [(0.5, 0.5)] # center
val = np.zeros((g.rows, g.cols), dtype=np.float32)
for ry, rx in sources:
dy = g.rr - g.rows * ry
dx = g.cc - g.cols * rx
d = np.sqrt(dy**2 + dx**2)
val += np.sin(d * freq - t * 4) * np.exp(-d * damping) * 0.5
return np.clip(val + 0.5, 0, 1)
```
---
## Particle Systems
### General Pattern
All particle systems use persistent state:
```python
S = state # dict persisted across frames
if "px" not in S:
S["px"]=[]; S["py"]=[]; S["vx"]=[]; S["vy"]=[]; S["life"]=[]; S["char"]=[]
# Emit new particles (on beat, continuously, or on trigger)
# Update: position += velocity, apply forces, decay life
# Draw: map to grid, set char/color based on life
# Cull: remove dead, cap total count
```
### Particle Character Sets
Don't hardcode particle chars. Choose per project/mood:
```python
# Energy / explosive
PART_ENERGY = list("*+#@\u26a1\u2726\u2605\u2588\u2593")
PART_SPARK = list("\u00b7\u2022\u25cf\u2605\u2736*+")
# Organic / natural
PART_LEAF = list("\u2740\u2741\u2742\u2743\u273f\u2618\u2022")
PART_SNOW = list("\u2744\u2745\u2746\u00b7\u2022*\u25cb")
PART_RAIN = list("|\u2502\u2503\u2551/\\")
PART_BUBBLE = list("\u25cb\u25ce\u25c9\u25cf\u2218\u2219\u00b0")
# Data / tech
PART_DATA = list("01{}[]<>|/\\")
PART_HEX = list("0123456789ABCDEF")
PART_BINARY = list("01")
# Mystical
PART_RUNE = list("\u16a0\u16a2\u16a6\u16b1\u16b7\u16c1\u16c7\u16d2\u16d6\u16da\u16de\u16df\u2726\u2605")
PART_ZODIAC = list("\u2648\u2649\u264a\u264b\u264c\u264d\u264e\u264f\u2650\u2651\u2652\u2653")
# Minimal
PART_DOT = list("\u00b7\u2022\u25cf")
PART_DASH = list("-=~\u2500\u2550")
```
### Explosion (Beat-Triggered)
```python
def emit_explosion(S, f, center_r, center_c, char_set=PART_ENERGY, count_base=80):
if f.get("beat", 0) > 0:
for _ in range(int(count_base + f["rms"]*150)):
ang = random.uniform(0, 2*math.pi)
sp = random.uniform(1, 9) * (0.5 + f.get("sub_r", 0.3)*2)
S["px"].append(float(center_c))
S["py"].append(float(center_r))
S["vx"].append(math.cos(ang)*sp*2.5)
S["vy"].append(math.sin(ang)*sp)
S["life"].append(1.0)
S["char"].append(random.choice(char_set))
# Update: gravity on vy += 0.03, life -= 0.015
# Color: life * 255 for brightness, hue fade controlled by caller
```
### Rising Embers
```python
# Emit: sy = rows-1, vy = -random.uniform(1,5), vx = random.uniform(-1.5,1.5)
# Update: vx += random jitter * 0.3, life -= 0.01
# Cap at ~1500 particles
```
### Dissolving Cloud
```python
# Init: N=600 particles spread across screen
# Update: slow upward drift, fade life progressively
# life -= 0.002 * (1 + elapsed * 0.05) # accelerating fade
```
### Starfield (3D Projection)
```python
# N stars with (sx, sy, sz) in normalized coords
# Move: sz -= speed (stars approach camera)
# Project: px = cx + sx/sz * cx, py = cy + sy/sz * cy
# Reset stars that pass camera (sz <= 0.01)
# Brightness = (1 - sz), draw streaks behind bright stars
```
### Orbit (Circular/Elliptical Motion)
```python
def emit_orbit(S, n=20, radius=15, speed=1.0, char_set=PART_DOT):
"""Particles orbiting a center point."""
for i in range(n):
angle = i * 2 * math.pi / n
S["px"].append(0.0); S["py"].append(0.0) # will be computed from angle
S["vx"].append(angle) # store angle as "vx" for orbit
S["vy"].append(radius + random.uniform(-2, 2)) # store radius
S["life"].append(1.0)
S["char"].append(random.choice(char_set))
# Update: angle += speed * dt, px = cx + radius * cos(angle), py = cy + radius * sin(angle)
```
### Gravity Well
```python
# Particles attracted toward one or more gravity points
# Update: compute force vector toward each well, apply as acceleration
# Particles that reach well center respawn at edges
```
---
## Rain / Matrix Effects
### Column Rain (Vectorized)
```python
def eff_matrix_rain(g, f, t, state, hue=0.33, bri=0.6, pal=PAL_KATA,
speed_base=0.5, speed_beat=3.0):
"""Vectorized matrix rain. state dict persists column positions."""
if "ry" not in state or len(state["ry"]) != g.cols:
state["ry"] = np.random.uniform(-g.rows, g.rows, g.cols).astype(np.float32)
state["rsp"] = np.random.uniform(0.3, 2.0, g.cols).astype(np.float32)
state["rln"] = np.random.randint(8, 40, g.cols)
state["rch"] = np.random.randint(0, len(pal), (g.rows, g.cols)) # pre-assign chars
speed_mult = speed_base + f.get("bass", 0.3)*speed_beat + f.get("sub_r", 0.3)*3
if f.get("beat", 0) > 0: speed_mult *= 2.5
state["ry"] += state["rsp"] * speed_mult
# Reset columns that fall past bottom
rst = (state["ry"] - state["rln"]) > g.rows
state["ry"][rst] = np.random.uniform(-25, -2, rst.sum())
# Vectorized draw using fancy indexing
ch = np.full((g.rows, g.cols), " ", dtype="U1")
co = np.zeros((g.rows, g.cols, 3), dtype=np.uint8)
heads = state["ry"].astype(int)
for c in range(g.cols):
head = heads[c]
trail_len = state["rln"][c]
for i in range(trail_len):
row = head - i
if 0 <= row < g.rows:
fade = 1.0 - i / trail_len
ci = state["rch"][row, c] % len(pal)
ch[row, c] = pal[ci]
v = fade * bri * 255
if i == 0: # head is bright white-ish
co[row, c] = (int(v*0.9), int(min(255, v*1.1)), int(v*0.9))
else:
R, G, B = hsv2rgb_single(hue, 0.7, fade * bri)
co[row, c] = (R, G, B)
return ch, co, state
```
---
## Glitch / Data Effects
### Horizontal Band Displacement
```python
def eff_glitch_displace(ch, co, f, intensity=1.0):
n_bands = int(8 + f.get("flux", 0.3)*25 + f.get("bdecay", 0)*15) * intensity
for _ in range(int(n_bands)):
y = random.randint(0, ch.shape[0]-1)
h = random.randint(1, int(3 + f.get("sub", 0.3)*8))
shift = int((random.random()-0.5) * f.get("rms", 0.3)*40 + f.get("bdecay", 0)*20*(random.random()-0.5))
if shift != 0:
for row in range(h):
rr = y + row
if 0 <= rr < ch.shape[0]:
ch[rr] = np.roll(ch[rr], shift)
co[rr] = np.roll(co[rr], shift, axis=0)
return ch, co
```
### Block Corruption
```python
def eff_block_corrupt(ch, co, f, char_pool=None, count_base=20):
if char_pool is None:
char_pool = list(PAL_BLOCKS[4:] + PAL_KATA[2:8])
for _ in range(int(count_base + f.get("flux", 0.3)*60 + f.get("bdecay", 0)*40)):
bx = random.randint(0, max(1, ch.shape[1]-6))
by = random.randint(0, max(1, ch.shape[0]-4))
bw, bh = random.randint(2,6), random.randint(1,4)
block_char = random.choice(char_pool)
# Fill rectangle with single char and random color
for r in range(bh):
for c in range(bw):
rr, cc = by+r, bx+c
if 0 <= rr < ch.shape[0] and 0 <= cc < ch.shape[1]:
ch[rr, cc] = block_char
co[rr, cc] = (random.randint(100,255), random.randint(0,100), random.randint(0,80))
return ch, co
```
### Scan Bars (Vertical)
```python
def eff_scanbars(ch, co, f, t, n_base=4, chars="|\u2551|!1l"):
for bi in range(int(n_base + f.get("himid_r", 0.3)*12)):
sx = int((t*50*(1+bi*0.3) + bi*37) % ch.shape[1])
for rr in range(ch.shape[0]):
if random.random() < 0.7:
ch[rr, sx] = random.choice(chars)
return ch, co
```
### Error Messages
```python
# Parameterize the error vocabulary per project:
ERRORS_TECH = ["SEGFAULT","0xDEADBEEF","BUFFER_OVERRUN","PANIC!","NULL_PTR",
"CORRUPT","SIGSEGV","ERR_OVERFLOW","STACK_SMASH","BAD_ALLOC"]
ERRORS_COSMIC = ["VOID_BREACH","ENTROPY_MAX","SINGULARITY","DIMENSION_FAULT",
"REALITY_ERR","TIME_PARADOX","DARK_MATTER_LEAK","QUANTUM_DECOHERE"]
ERRORS_ORGANIC = ["CELL_DIVISION_ERR","DNA_MISMATCH","MUTATION_OVERFLOW",
"NEURAL_DEADLOCK","SYNAPSE_TIMEOUT","MEMBRANE_BREACH"]
```
### Hex Data Stream
```python
hex_str = "".join(random.choice("0123456789ABCDEF") for _ in range(random.randint(8,20)))
stamp(ch, co, hex_str, rand_row, rand_col, (0, 160, 80))
```
---
## Spectrum / Visualization
### Mirrored Spectrum Bars
```python
def eff_spectrum(g, f, t, n_bars=64, pal=PAL_BLOCKS, mirror=True):
bar_w = max(1, g.cols // n_bars); mid = g.rows // 2
band_vals = np.array([f.get("sub",0.3), f.get("bass",0.3), f.get("lomid",0.3),
f.get("mid",0.3), f.get("himid",0.3), f.get("hi",0.3)])
ch = np.full((g.rows, g.cols), " ", dtype="U1")
co = np.zeros((g.rows, g.cols, 3), dtype=np.uint8)
for b in range(n_bars):
frac = b / n_bars
fi = frac * 5; lo_i = int(fi); hi_i = min(lo_i+1, 5)
bval = min(1, (band_vals[lo_i]*(1-fi%1) + band_vals[hi_i]*(fi%1)) * 1.8)
height = int(bval * (g.rows//2 - 2))
for dy in range(height):
hue = (f.get("cent",0.5)*0.3 + frac*0.3 + dy/max(height,1)*0.15) % 1.0
ci = pal[min(int(dy/max(height,1)*len(pal)*0.7+len(pal)*0.2), len(pal)-1)]
for dc in range(bar_w - (1 if bar_w > 2 else 0)):
cc = b*bar_w + dc
if 0 <= cc < g.cols:
rows_to_draw = [mid - dy, mid + dy] if mirror else [g.rows - 1 - dy]
for row in rows_to_draw:
if 0 <= row < g.rows:
ch[row, cc] = ci
co[row, cc] = hsv_to_rgb_single(hue, 0.85, 0.5+dy/max(height,1)*0.5)
return ch, co
```
### Waveform
```python
def eff_waveform(g, f, t, row_offset=-5, hue=0.1):
ch = np.full((g.rows, g.cols), " ", dtype="U1")
co = np.zeros((g.rows, g.cols, 3), dtype=np.uint8)
for c in range(g.cols):
wv = (math.sin(c*0.15+t*5)*f.get("bass",0.3)*0.5
+ math.sin(c*0.3+t*8)*f.get("mid",0.3)*0.3
+ math.sin(c*0.6+t*12)*f.get("hi",0.3)*0.15)
wr = g.rows + row_offset + int(wv * 4)
if 0 <= wr < g.rows:
ch[wr, c] = "~"
v = int(120 + f.get("rms",0.3)*135)
co[wr, c] = [v, int(v*0.7), int(v*0.4)]
return ch, co
```
---
## Fire / Lava
### Fire Columns
```python
def eff_fire(g, f, t, n_base=20, hue_base=0.02, hue_range=0.12, pal=PAL_BLOCKS):
n_cols = int(n_base + f.get("bass",0.3)*30 + f.get("sub_r",0.3)*20)
ch = np.full((g.rows, g.cols), " ", dtype="U1")
co = np.zeros((g.rows, g.cols, 3), dtype=np.uint8)
for fi in range(n_cols):
fx_c = int((fi*g.cols/n_cols + np.sin(t*2+fi*0.7)*3) % g.cols)
height = int((f.get("bass",0.3)*0.4 + f.get("sub_r",0.3)*0.3 + f.get("rms",0.3)*0.3) * g.rows * 0.7)
for dy in range(min(height, g.rows)):
fr = g.rows - 1 - dy
frac = dy / max(height, 1)
bri = max(0.1, (1 - frac*0.6) * (0.5 + f.get("rms",0.3)*0.5))
hue = hue_base + frac * hue_range
ci = "\u2588" if frac<0.2 else ("\u2593" if frac<0.4 else ("\u2592" if frac<0.6 else "\u2591"))
ch[fr, fx_c] = ci
R, G, B = hsv2rgb_single(hue, 0.9, bri)
co[fr, fx_c] = (R, G, B)
return ch, co
```
### Ice / Cold Fire (same structure, different hue range)
```python
# hue_base=0.55, hue_range=0.15 -- blue to cyan
# Lower intensity, slower movement
```
---
## Text Overlays
### Scrolling Ticker
```python
def eff_ticker(ch, co, t, text, row, speed=15, color=(80, 100, 140)):
off = int(t * speed) % max(len(text), 1)
doubled = text + " " + text
stamp(ch, co, doubled[off:off+ch.shape[1]], row, 0, color)
```
### Beat-Triggered Words
```python
def eff_beat_words(ch, co, f, words, row_center=None, color=(255,240,220)):
if f.get("beat", 0) > 0:
w = random.choice(words)
r = (row_center or ch.shape[0]//2) + random.randint(-5,5)
stamp(ch, co, w, r, (ch.shape[1]-len(w))//2, color)
```
### Fading Message Sequence
```python
def eff_fading_messages(ch, co, t, elapsed, messages, period=4.0, color_base=(220,220,220)):
msg_idx = int(elapsed / period) % len(messages)
phase = elapsed % period
fade = max(0, min(1.0, phase) * min(1.0, period - phase))
if fade > 0.05:
v = fade
msg = messages[msg_idx]
cr, cg, cb = [int(c * v) for c in color_base]
stamp(ch, co, msg, ch.shape[0]//2, (ch.shape[1]-len(msg))//2, (cr, cg, cb))
```
---
## Screen Shake
Shift entire char/color arrays on beat:
```python
def eff_shake(ch, co, f, x_amp=6, y_amp=3):
shake_x = int(f.get("sub",0.3)*x_amp*(random.random()-0.5)*2 + f.get("bdecay",0)*4*(random.random()-0.5)*2)
shake_y = int(f.get("bass",0.3)*y_amp*(random.random()-0.5)*2)
if abs(shake_x) > 0:
ch = np.roll(ch, shake_x, axis=1)
co = np.roll(co, shake_x, axis=1)
if abs(shake_y) > 0:
ch = np.roll(ch, shake_y, axis=0)
co = np.roll(co, shake_y, axis=0)
return ch, co
```
---
## Composable Effect System
The real creative power comes from **composition**. There are three levels:
### Level 1: Character-Level Layering
Stack multiple effects as `(chars, colors)` layers:
```python
class LayerStack(EffectNode):
"""Render effects bottom-to-top with character-level compositing."""
def add(self, effect, alpha=1.0):
"""alpha < 1.0 = probabilistic override (sparse overlay)."""
self.layers.append((effect, alpha))
# Usage:
stack = LayerStack()
stack.add(bg_effect) # base — fills screen
stack.add(main_effect) # overlay on top (space chars = transparent)
stack.add(particle_effect) # sparse overlay on top of that
ch, co = stack.render(g, f, t, S)
```
### Level 2: Pixel-Level Blending
After rendering to canvases, blend with Photoshop-style modes:
```python
class PixelBlendStack:
"""Stack canvases with blend modes for complex compositing."""
def add(self, canvas, mode="normal", opacity=1.0)
def composite(self) -> canvas
# Usage:
pbs = PixelBlendStack()
pbs.add(canvas_a) # base
pbs.add(canvas_b, "screen", 0.7) # additive glow
pbs.add(canvas_c, "difference", 0.5) # psychedelic interference
result = pbs.composite()
```
### Level 3: Temporal Feedback
Feed previous frame back into current frame for recursive effects:
```python
fb = FeedbackBuffer()
for each frame:
canvas = render_current()
canvas = fb.apply(canvas, decay=0.8, blend="screen",
transform="zoom", transform_amt=0.015, hue_shift=0.02)
```
### Effect Nodes — Uniform Interface
In the v2 protocol, effect nodes are used **inside** scene functions. The scene function itself returns a canvas. Effect nodes produce intermediate `(chars, colors)` that are rendered to canvas via the grid's `.render()` method or `_render_vf()`.
```python
class EffectNode:
def render(self, g, f, t, S) -> (chars, colors)
# Concrete implementations:
class ValueFieldEffect(EffectNode):
"""Wraps a value field function + hue field function + palette."""
def __init__(self, val_fn, hue_fn, pal=PAL_DEFAULT, sat=0.7)
class LambdaEffect(EffectNode):
"""Wrap any (g,f,t,S) -> (ch,co) function."""
def __init__(self, fn)
class ConditionalEffect(EffectNode):
"""Switch effects based on audio features."""
def __init__(self, condition, if_true, if_false=None)
```
### Value Field Generators (Atomic Building Blocks)
These produce float32 arrays `(rows, cols)` in range [0,1]. They are the raw visual patterns. All have signature `(g, f, t, S, **params) -> float32 array`.
```python
def vf_sinefield(g, f, t, S, bri=0.5,
freq=(0.13, 0.17, 0.07, 0.09), speed=(0.5, -0.4, -0.3, 0.2)):
"""Layered sine field. General purpose background/texture."""
v1 = np.sin(g.cc*freq[0] + t*speed[0]) * np.sin(g.rr*freq[1] - t*speed[1]) * 0.5 + 0.5
v2 = np.sin(g.cc*freq[2] - t*speed[2] + g.rr*freq[3]) * 0.4 + 0.5
v3 = np.sin(g.dist_n*5 + t*0.2) * 0.3 + 0.4
return np.clip((v1*0.35 + v2*0.35 + v3*0.3) * bri * (0.6 + f.get("rms",0.3)*0.6), 0, 1)
def vf_smooth_noise(g, f, t, S, octaves=3, bri=0.5):
"""Multi-octave sine approximation of Perlin noise."""
val = np.zeros((g.rows, g.cols), dtype=np.float32)
for i in range(octaves):
freq = 0.05 * (2 ** i); amp = 0.5 / (i + 1)
phase = t * (0.3 + i * 0.2)
val = val + np.sin(g.cc*freq + phase) * np.cos(g.rr*freq*0.7 - phase*0.5) * amp
return np.clip(val * 0.5 + 0.5, 0, 1) * bri
def vf_rings(g, f, t, S, n_base=6, spacing_base=4):
"""Concentric rings, bass-driven count and wobble."""
n = int(n_base + f.get("sub_r",0.3)*25 + f.get("bass",0.3)*10)
sp = spacing_base + f.get("bass_r",0.3)*7 + f.get("rms",0.3)*3
val = np.zeros((g.rows, g.cols), dtype=np.float32)
for ri in range(n):
rad = (ri+1)*sp + f.get("bdecay",0)*15
wobble = f.get("mid_r",0.3)*5*np.sin(g.angle*3+t*4)
rd = np.abs(g.dist - rad - wobble)
th = 1 + f.get("sub",0.3)*3
val = np.maximum(val, np.clip((1 - rd/th) * (0.4 + f.get("bass",0.3)*0.8), 0, 1))
return val
def vf_spiral(g, f, t, S, n_arms=3, tightness=2.5):
"""Logarithmic spiral arms."""
val = np.zeros((g.rows, g.cols), dtype=np.float32)
for ai in range(n_arms):
offset = ai * 2*np.pi / n_arms
log_r = np.log(g.dist + 1) * tightness
arm_phase = g.angle + offset - log_r + t * 0.8
arm_val = np.clip(np.cos(arm_phase * n_arms) * 0.6 + 0.2, 0, 1)
arm_val *= (0.4 + f.get("rms",0.3)*0.6) * np.clip(1 - g.dist_n*0.5, 0.2, 1)
val = np.maximum(val, arm_val)
return val
def vf_tunnel(g, f, t, S, speed=3.0, complexity=6):
"""Tunnel depth effect — infinite zoom feeling."""
tunnel_d = 1.0 / (g.dist_n + 0.1)
v1 = np.sin(tunnel_d*2 - t*speed) * 0.45 + 0.55
v2 = np.sin(g.angle*complexity + tunnel_d*1.5 - t*2) * 0.35 + 0.55
return np.clip(v1*0.5 + v2*0.5, 0, 1)
def vf_vortex(g, f, t, S, twist=3.0):
"""Twisting radial pattern — distance modulates angle."""
twisted = g.angle + g.dist_n * twist * np.sin(t * 0.5)
val = np.sin(twisted * 4 - t * 2) * 0.5 + 0.5
return np.clip(val * (0.5 + f.get("bass",0.3)*0.8), 0, 1)
def vf_interference(g, f, t, S, n_waves=6):
"""Overlapping sine waves creating moire patterns."""
drivers = ["mid_r", "himid_r", "bass_r", "lomid_r", "hi_r", "sub_r"]
vals = np.zeros((g.rows, g.cols), dtype=np.float32)
for i in range(min(n_waves, len(drivers))):
angle = i * np.pi / n_waves
freq = 0.06 + i * 0.03; sp = 0.5 + i * 0.3
proj = g.cc * np.cos(angle) + g.rr * np.sin(angle)
vals = vals + np.sin(proj*freq + t*sp) * f.get(drivers[i], 0.3) * 2.5
return np.clip(vals * 0.12 + 0.45, 0.1, 1)
def vf_aurora(g, f, t, S, n_bands=3):
"""Horizontal aurora bands."""
val = np.zeros((g.rows, g.cols), dtype=np.float32)
for i in range(n_bands):
fr = 0.08 + i*0.04; fc = 0.012 + i*0.008
sr = 0.7 + i*0.3; sc = 0.18 + i*0.12
val = val + np.sin(g.rr*fr + t*sr) * np.sin(g.cc*fc + t*sc) * (0.6/n_bands)
return np.clip(val * (f.get("lomid_r",0.3)*3 + 0.2), 0, 0.7)
def vf_ripple(g, f, t, S, sources=None, freq=0.3, damping=0.02):
"""Concentric ripples from point sources."""
if sources is None: sources = [(0.5, 0.5)]
val = np.zeros((g.rows, g.cols), dtype=np.float32)
for ry, rx in sources:
dy = g.rr - g.rows*ry; dx = g.cc - g.cols*rx
d = np.sqrt(dy**2 + dx**2)
val = val + np.sin(d*freq - t*4) * np.exp(-d*damping) * 0.5
return np.clip(val + 0.5, 0, 1)
def vf_plasma(g, f, t, S):
"""Classic plasma: sum of sines at different orientations and speeds."""
v = np.sin(g.cc * 0.03 + t * 0.7) * 0.5
v = v + np.sin(g.rr * 0.04 - t * 0.5) * 0.4
v = v + np.sin((g.cc * 0.02 + g.rr * 0.03) + t * 0.3) * 0.3
v = v + np.sin(g.dist_n * 4 - t * 0.8) * 0.3
return np.clip(v * 0.5 + 0.5, 0, 1)
def vf_diamond(g, f, t, S, freq=0.15):
"""Diamond/checkerboard pattern."""
val = np.abs(np.sin(g.cc * freq + t * 0.5)) * np.abs(np.sin(g.rr * freq * 1.2 - t * 0.3))
return np.clip(val * (0.6 + f.get("rms",0.3)*0.8), 0, 1)
def vf_noise_static(g, f, t, S, density=0.4):
"""Random noise — different each frame. Non-deterministic."""
return np.random.random((g.rows, g.cols)).astype(np.float32) * density * (0.5 + f.get("rms",0.3)*0.5)
```
### Hue Field Generators (Color Mapping)
These produce float32 hue arrays [0,1]. Independently combinable with any value field. Each is a factory returning a closure with signature `(g, f, t, S) -> float32 array`. Can also be a plain float for fixed hue.
```python
def hf_fixed(hue):
"""Single hue everywhere."""
def fn(g, f, t, S):
return np.full((g.rows, g.cols), hue, dtype=np.float32)
return fn
def hf_angle(offset=0.0):
"""Hue mapped to angle from center — rainbow wheel."""
def fn(g, f, t, S):
return (g.angle / (2 * np.pi) + offset + t * 0.05) % 1.0
return fn
def hf_distance(base=0.5, scale=0.02):
"""Hue mapped to distance from center."""
def fn(g, f, t, S):
return (base + g.dist * scale + t * 0.03) % 1.0
return fn
def hf_time_cycle(speed=0.1):
"""Hue cycles uniformly over time."""
def fn(g, f, t, S):
return np.full((g.rows, g.cols), (t * speed) % 1.0, dtype=np.float32)
return fn
def hf_audio_cent():
"""Hue follows spectral centroid — timbral color shifting."""
def fn(g, f, t, S):
return np.full((g.rows, g.cols), f.get("cent", 0.5) * 0.3, dtype=np.float32)
return fn
def hf_gradient_h(start=0.0, end=1.0):
"""Left-to-right hue gradient."""
def fn(g, f, t, S):
h = np.broadcast_to(
start + (g.cc / g.cols) * (end - start),
(g.rows, g.cols)
).copy() # .copy() is CRITICAL — see troubleshooting.md
return h % 1.0
return fn
def hf_gradient_v(start=0.0, end=1.0):
"""Top-to-bottom hue gradient."""
def fn(g, f, t, S):
h = np.broadcast_to(
start + (g.rr / g.rows) * (end - start),
(g.rows, g.cols)
).copy()
return h % 1.0
return fn
def hf_plasma(speed=0.3):
"""Plasma-style hue field — organic color variation."""
def fn(g, f, t, S):
return (np.sin(g.cc*0.02 + t*speed)*0.5 + np.sin(g.rr*0.015 + t*speed*0.7)*0.5) % 1.0
return fn
```
### Combining Value Fields
The combinatorial explosion comes from mixing value fields with math:
```python
# Multiplication = intersection (only shows where both have brightness)
combined = vf_plasma(g,f,t,S) * vf_vortex(g,f,t,S)
# Addition = union (shows both, clips at 1.0)
combined = np.clip(vf_rings(g,f,t,S) + vf_spiral(g,f,t,S), 0, 1)
# Interference = beat pattern (shows XOR-like patterns)
combined = np.abs(vf_plasma(g,f,t,S) - vf_tunnel(g,f,t,S))
# Modulation = one effect shapes the other
combined = vf_rings(g,f,t,S) * (0.3 + 0.7 * vf_plasma(g,f,t,S))
# Maximum = shows the brightest of two effects
combined = np.maximum(vf_spiral(g,f,t,S), vf_aurora(g,f,t,S))
```
### Full Scene Example (v2 — Canvas Return)
A v2 scene function composes effects internally and returns a pixel canvas:
```python
def scene_complex(r, f, t, S):
"""v2 scene function: returns canvas (uint8 H,W,3).
r = Renderer, f = audio features, t = time, S = persistent state dict."""
g = r.grids["md"]
rows, cols = g.rows, g.cols
# 1. Value field composition
plasma = vf_plasma(g, f, t, S)
vortex = vf_vortex(g, f, t, S, twist=4.0)
combined = np.clip(plasma * 0.6 + vortex * 0.5 + plasma * vortex * 0.4, 0, 1)
# 2. Color from hue field
h = (hf_angle(0.3)(g,f,t,S) * 0.5 + hf_time_cycle(0.08)(g,f,t,S) * 0.5) % 1.0
# 3. Render to canvas via _render_vf helper
canvas = _render_vf(g, combined, h, sat=0.75, pal=PAL_DENSE)
# 4. Optional: blend a second layer
overlay = _render_vf(r.grids["sm"], vf_rings(r.grids["sm"],f,t,S),
hf_fixed(0.6)(r.grids["sm"],f,t,S), pal=PAL_BLOCK)
canvas = blend_canvas(canvas, overlay, "screen", 0.4)
return canvas
# In the render_clip() loop (handled by the framework):
# canvas = scene_fn(r, f, t, S)
# canvas = tonemap(canvas, gamma=scene_gamma)
# canvas = feedback.apply(canvas, ...)
# canvas = shader_chain.apply(canvas, f=f, t=t)
# pipe.stdin.write(canvas.tobytes())
```
Vary the **value field combo**, **hue field**, **palette**, **blend modes**, **feedback config**, and **shader chain** per section for maximum visual variety. With 12 value fields × 8 hue fields × 14 palettes × 20 blend modes × 7 feedback transforms × 38 shaders, the combinations are effectively infinite.

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# Input Sources
## Audio Analysis
### Loading
```python
tmp = tempfile.mktemp(suffix=".wav")
subprocess.run(["ffmpeg", "-y", "-i", input_path, "-ac", "1", "-ar", "22050",
"-sample_fmt", "s16", tmp], capture_output=True, check=True)
with wave.open(tmp) as wf:
sr = wf.getframerate()
raw = wf.readframes(wf.getnframes())
samples = np.frombuffer(raw, dtype=np.int16).astype(np.float32) / 32768.0
```
### Per-Frame FFT
```python
hop = sr // fps # samples per frame
win = hop * 2 # analysis window (2x hop for overlap)
window = np.hanning(win)
freqs = rfftfreq(win, 1.0 / sr)
bands = {
"sub": (freqs >= 20) & (freqs < 80),
"bass": (freqs >= 80) & (freqs < 250),
"lomid": (freqs >= 250) & (freqs < 500),
"mid": (freqs >= 500) & (freqs < 2000),
"himid": (freqs >= 2000)& (freqs < 6000),
"hi": (freqs >= 6000),
}
```
For each frame: extract chunk, apply window, FFT, compute band energies.
### Feature Set
| Feature | Formula | Controls |
|---------|---------|----------|
| `rms` | `sqrt(mean(chunk²))` | Overall loudness/energy |
| `sub`..`hi` | `sqrt(mean(band_magnitudes²))` | Per-band energy |
| `centroid` | `sum(freq*mag) / sum(mag)` | Brightness/timbre |
| `flatness` | `geomean(mag) / mean(mag)` | Noise vs tone |
| `flux` | `sum(max(0, mag - prev_mag))` | Transient strength |
| `sub_r`..`hi_r` | `band / sum(all_bands)` | Spectral shape (volume-independent) |
| `cent_d` | `abs(gradient(centroid))` | Timbral change rate |
| `beat` | Flux peak detection | Binary beat onset |
| `bdecay` | Exponential decay from beats | Smooth beat pulse (0→1→0) |
**Band ratios are critical** — they decouple spectral shape from volume, so a quiet bass section and a loud bass section both read as "bassy" rather than just "loud" vs "quiet".
### Smoothing
EMA prevents visual jitter:
```python
def ema(arr, alpha):
out = np.empty_like(arr); out[0] = arr[0]
for i in range(1, len(arr)):
out[i] = alpha * arr[i] + (1 - alpha) * out[i-1]
return out
# Slow-moving features (alpha=0.12): centroid, flatness, band ratios, cent_d
# Fast-moving features (alpha=0.3): rms, flux, raw bands
```
### Beat Detection
```python
flux_smooth = np.convolve(flux, np.ones(5)/5, mode="same")
peaks, _ = signal.find_peaks(flux_smooth, height=0.15, distance=fps//5, prominence=0.05)
beat = np.zeros(n_frames)
bdecay = np.zeros(n_frames, dtype=np.float32)
for p in peaks:
beat[p] = 1.0
for d in range(fps // 2):
if p + d < n_frames:
bdecay[p + d] = max(bdecay[p + d], math.exp(-d * 2.5 / (fps // 2)))
```
`bdecay` gives smooth 0→1→0 pulse per beat, decaying over ~0.5s. Use for flash/glitch/mirror triggers.
### Normalization
After computing all frames, normalize each feature to 0-1:
```python
for k in features:
a = features[k]
lo, hi = a.min(), a.max()
features[k] = (a - lo) / (hi - lo + 1e-10)
```
## Video Sampling
### Frame Extraction
```python
# Method 1: ffmpeg pipe (memory efficient)
cmd = ["ffmpeg", "-i", input_video, "-f", "rawvideo", "-pix_fmt", "rgb24",
"-s", f"{target_w}x{target_h}", "-r", str(fps), "-"]
pipe = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.DEVNULL)
frame_size = target_w * target_h * 3
for fi in range(n_frames):
raw = pipe.stdout.read(frame_size)
if len(raw) < frame_size: break
frame = np.frombuffer(raw, dtype=np.uint8).reshape(target_h, target_w, 3)
# process frame...
# Method 2: OpenCV (if available)
cap = cv2.VideoCapture(input_video)
```
### Luminance-to-Character Mapping
Convert video pixels to ASCII characters based on brightness:
```python
def frame_to_ascii(frame_rgb, grid, pal=PAL_DEFAULT):
"""Convert video frame to character + color arrays."""
rows, cols = grid.rows, grid.cols
# Resize frame to grid dimensions
small = np.array(Image.fromarray(frame_rgb).resize((cols, rows), Image.LANCZOS))
# Luminance
lum = (0.299 * small[:,:,0] + 0.587 * small[:,:,1] + 0.114 * small[:,:,2]) / 255.0
# Map to chars
chars = val2char(lum, lum > 0.02, pal)
# Colors: use source pixel colors, scaled by luminance for visibility
colors = np.clip(small * np.clip(lum[:,:,None] * 1.5 + 0.3, 0.3, 1), 0, 255).astype(np.uint8)
return chars, colors
```
### Edge-Weighted Character Mapping
Use edge detection for more detail in contour regions:
```python
def frame_to_ascii_edges(frame_rgb, grid, pal=PAL_DEFAULT, edge_pal=PAL_BOX):
gray = np.mean(frame_rgb, axis=2)
small_gray = resize(gray, (grid.rows, grid.cols))
lum = small_gray / 255.0
# Sobel edge detection
gx = np.abs(small_gray[:, 2:] - small_gray[:, :-2])
gy = np.abs(small_gray[2:, :] - small_gray[:-2, :])
edge = np.zeros_like(small_gray)
edge[:, 1:-1] += gx; edge[1:-1, :] += gy
edge = np.clip(edge / edge.max(), 0, 1)
# Edge regions get box drawing chars, flat regions get brightness chars
is_edge = edge > 0.15
chars = val2char(lum, lum > 0.02, pal)
edge_chars = val2char(edge, is_edge, edge_pal)
chars[is_edge] = edge_chars[is_edge]
return chars, colors
```
### Motion Detection
Detect pixel changes between frames for motion-reactive effects:
```python
prev_frame = None
def compute_motion(frame):
global prev_frame
if prev_frame is None:
prev_frame = frame.astype(np.float32)
return np.zeros(frame.shape[:2])
diff = np.abs(frame.astype(np.float32) - prev_frame).mean(axis=2)
prev_frame = frame.astype(np.float32) * 0.7 + prev_frame * 0.3 # smoothed
return np.clip(diff / 30.0, 0, 1) # normalized motion map
```
Use motion map to drive particle emission, glitch intensity, or character density.
### Video Feature Extraction
Per-frame features analogous to audio features, for driving effects:
```python
def analyze_video_frame(frame_rgb):
gray = np.mean(frame_rgb, axis=2)
return {
"brightness": gray.mean() / 255.0,
"contrast": gray.std() / 128.0,
"edge_density": compute_edge_density(gray),
"motion": compute_motion(frame_rgb).mean(),
"dominant_hue": compute_dominant_hue(frame_rgb),
"color_variance": compute_color_variance(frame_rgb),
}
```
## Image Sequence
### Static Image to ASCII
Same as single video frame conversion. For animated sequences:
```python
import glob
frames = sorted(glob.glob("frames/*.png"))
for fi, path in enumerate(frames):
img = np.array(Image.open(path).resize((VW, VH)))
chars, colors = frame_to_ascii(img, grid, pal)
```
### Image as Texture Source
Use an image as a background texture that effects modulate:
```python
def load_texture(path, grid):
img = np.array(Image.open(path).resize((grid.cols, grid.rows)))
lum = np.mean(img, axis=2) / 255.0
return lum, img # luminance for char mapping, RGB for colors
```
## Text / Lyrics
### SRT Parsing
```python
import re
def parse_srt(path):
"""Returns [(start_sec, end_sec, text), ...]"""
entries = []
with open(path) as f:
content = f.read()
blocks = content.strip().split("\n\n")
for block in blocks:
lines = block.strip().split("\n")
if len(lines) >= 3:
times = lines[1]
m = re.match(r"(\d+):(\d+):(\d+),(\d+) --> (\d+):(\d+):(\d+),(\d+)", times)
if m:
g = [int(x) for x in m.groups()]
start = g[0]*3600 + g[1]*60 + g[2] + g[3]/1000
end = g[4]*3600 + g[5]*60 + g[6] + g[7]/1000
text = " ".join(lines[2:])
entries.append((start, end, text))
return entries
```
### Lyrics Display Modes
- **Typewriter**: characters appear left-to-right over the time window
- **Fade-in**: whole line fades from dark to bright
- **Flash**: appear instantly on beat, fade out
- **Scatter**: characters start at random positions, converge to final position
- **Wave**: text follows a sine wave path
```python
def lyrics_typewriter(ch, co, text, row, col, t, t_start, t_end, color):
"""Reveal characters progressively over time window."""
progress = np.clip((t - t_start) / (t_end - t_start), 0, 1)
n_visible = int(len(text) * progress)
stamp(ch, co, text[:n_visible], row, col, color)
```
## Generative (No Input)
For pure generative ASCII art, the "features" dict is synthesized from time:
```python
def synthetic_features(t, bpm=120):
"""Generate audio-like features from time alone."""
beat_period = 60.0 / bpm
beat_phase = (t % beat_period) / beat_period
return {
"rms": 0.5 + 0.3 * math.sin(t * 0.5),
"bass": 0.5 + 0.4 * math.sin(t * 2 * math.pi / beat_period),
"sub": 0.3 + 0.3 * math.sin(t * 0.8),
"mid": 0.4 + 0.3 * math.sin(t * 1.3),
"hi": 0.3 + 0.2 * math.sin(t * 2.1),
"cent": 0.5 + 0.2 * math.sin(t * 0.3),
"flat": 0.4,
"flux": 0.3 + 0.2 * math.sin(t * 3),
"beat": 1.0 if beat_phase < 0.05 else 0.0,
"bdecay": max(0, 1.0 - beat_phase * 4),
# ratios
"sub_r": 0.2, "bass_r": 0.25, "lomid_r": 0.15,
"mid_r": 0.2, "himid_r": 0.12, "hi_r": 0.08,
"cent_d": 0.1,
}
```
## TTS Integration
For narrated videos (testimonials, quotes, storytelling), generate speech audio per segment and mix with background music.
### ElevenLabs Voice Generation
```python
import requests
def generate_tts(text, voice_id, api_key, output_path, model="eleven_multilingual_v2"):
"""Generate TTS audio via ElevenLabs API."""
url = f"https://api.elevenlabs.io/v1/text-to-speech/{voice_id}"
headers = {"xi-api-key": api_key, "Content-Type": "application/json"}
data = {"text": text, "model_id": model,
"voice_settings": {"stability": 0.5, "similarity_boost": 0.75}}
resp = requests.post(url, json=data, headers=headers, timeout=30)
resp.raise_for_status()
with open(output_path, "wb") as f:
f.write(resp.content)
```
### Voice Assignment
Use multiple voices for variety. Shuffle deterministically so re-runs are consistent:
```python
import random as _rng
def assign_voices(n_quotes, voice_pool, seed=42):
"""Assign a different voice to each quote, cycling if needed."""
r = _rng.Random(seed)
shuffled = list(voice_pool)
r.shuffle(shuffled)
return [shuffled[i % len(shuffled)] for i in range(n_quotes)]
```
### Pronunciation Control
TTS text should be separate from display text. Common fixes:
- Brand names: spell phonetically ("Nous" -> "Noose", "nginx" -> "engine-x")
- Abbreviations: expand ("API" -> "A P I", "CLI" -> "C L I")
- Technical terms: add phonetic hints
```python
QUOTES = [("Display text here", "Author")]
QUOTES_TTS = ["TTS text with phonetic spelling here"]
# Keep both arrays in sync -- same indices
```
### Audio Pipeline
1. Generate individual TTS clips (MP3/WAV per quote)
2. Get duration of each clip
3. Calculate timing: speech start/end per quote with gaps
4. Concatenate into single TTS track with silence padding
5. Mix with background music
```python
def build_tts_track(tts_clips, target_duration, gap_seconds=2.0):
"""Concatenate TTS clips with gaps, pad to target duration."""
# Get durations
durations = []
for clip in tts_clips:
result = subprocess.run(
["ffprobe", "-v", "error", "-show_entries", "format=duration",
"-of", "csv=p=0", clip],
capture_output=True, text=True)
durations.append(float(result.stdout.strip()))
# Calculate timing
total_speech = sum(durations)
total_gaps = target_duration - total_speech
gap = max(0.5, total_gaps / (len(tts_clips) + 1))
timing = [] # (start, end, quote_index)
t = gap # start after initial gap
for i, dur in enumerate(durations):
timing.append((t, t + dur, i))
t += dur + gap
# Concatenate with ffmpeg
# ... silence padding + concat filter
return timing
```
### Audio Mixing
Mix TTS (center) with background music (wide stereo, low volume):
```python
def mix_audio(tts_path, bgm_path, output_path, bgm_volume=0.15):
"""Mix TTS centered with BGM panned wide stereo."""
cmd = [
"ffmpeg", "-y",
"-i", tts_path, # mono TTS
"-i", bgm_path, # stereo BGM
"-filter_complex",
f"[0:a]aformat=sample_fmts=fltp:sample_rates=44100:channel_layouts=mono,"
f"pan=stereo|c0=c0|c1=c0[tts];" # TTS center
f"[1:a]loudnorm=I=-16:TP=-1.5:LRA=11,"
f"volume={bgm_volume},"
f"extrastereo=2.5[bgm];" # BGM wide stereo
f"[tts][bgm]amix=inputs=2:duration=longest[out]",
"-map", "[out]", "-c:a", "pcm_s16le", output_path
]
subprocess.run(cmd, capture_output=True, check=True)
```
### Feature Analysis on Mixed Audio
Run the standard audio analysis (FFT, beat detection) on the final mixed track so visual effects react to both TTS and music:
```python
# Analyze mixed_final.wav (not individual tracks)
features = analyze_audio("mixed_final.wav", fps=24)
```
This means visuals will pulse with both the music beats and the speech energy -- creating natural synchronization.

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# Optimization Reference
## Hardware Detection
Detect the user's hardware at script startup and adapt rendering parameters automatically. Never hardcode worker counts or resolution.
### CPU and Memory Detection
```python
import multiprocessing
import platform
import shutil
import os
def detect_hardware():
"""Detect hardware capabilities and return render config."""
cpu_count = multiprocessing.cpu_count()
# Leave 1-2 cores free for OS + ffmpeg encoding
if cpu_count >= 16:
workers = cpu_count - 2
elif cpu_count >= 8:
workers = cpu_count - 1
elif cpu_count >= 4:
workers = cpu_count - 1
else:
workers = max(1, cpu_count)
# Memory detection (platform-specific)
try:
if platform.system() == "Darwin":
import subprocess
mem_bytes = int(subprocess.check_output(["sysctl", "-n", "hw.memsize"]).strip())
elif platform.system() == "Linux":
with open("/proc/meminfo") as f:
for line in f:
if line.startswith("MemTotal"):
mem_bytes = int(line.split()[1]) * 1024
break
else:
mem_bytes = 8 * 1024**3 # assume 8GB on unknown
except Exception:
mem_bytes = 8 * 1024**3
mem_gb = mem_bytes / (1024**3)
# Each worker uses ~50-150MB depending on grid sizes
# Cap workers if memory is tight
mem_per_worker_mb = 150
max_workers_by_mem = int(mem_gb * 1024 * 0.6 / mem_per_worker_mb) # use 60% of RAM
workers = min(workers, max_workers_by_mem)
# ffmpeg availability and codec support
has_ffmpeg = shutil.which("ffmpeg") is not None
return {
"cpu_count": cpu_count,
"workers": workers,
"mem_gb": mem_gb,
"platform": platform.system(),
"arch": platform.machine(),
"has_ffmpeg": has_ffmpeg,
}
```
### Adaptive Quality Profiles
Scale resolution, FPS, CRF, and grid density based on hardware:
```python
def quality_profile(hw, target_duration_s, user_preference="auto"):
"""
Returns render settings adapted to hardware.
user_preference: "auto", "draft", "preview", "production", "max"
"""
if user_preference == "draft":
return {"vw": 960, "vh": 540, "fps": 12, "crf": 28, "workers": min(4, hw["workers"]),
"grid_scale": 0.5, "shaders": "minimal", "particles_max": 200}
if user_preference == "preview":
return {"vw": 1280, "vh": 720, "fps": 15, "crf": 25, "workers": hw["workers"],
"grid_scale": 0.75, "shaders": "standard", "particles_max": 500}
if user_preference == "max":
return {"vw": 3840, "vh": 2160, "fps": 30, "crf": 15, "workers": hw["workers"],
"grid_scale": 2.0, "shaders": "full", "particles_max": 3000}
# "production" or "auto"
# Auto-detect: estimate render time, downgrade if it would take too long
n_frames = int(target_duration_s * 24)
est_seconds_per_frame = 0.18 # ~180ms at 1080p
est_total_s = n_frames * est_seconds_per_frame / max(1, hw["workers"])
if hw["mem_gb"] < 4 or hw["cpu_count"] <= 2:
# Low-end: 720p, 15fps
return {"vw": 1280, "vh": 720, "fps": 15, "crf": 23, "workers": hw["workers"],
"grid_scale": 0.75, "shaders": "standard", "particles_max": 500}
if est_total_s > 3600: # would take over an hour
# Downgrade to 720p to speed up
return {"vw": 1280, "vh": 720, "fps": 24, "crf": 20, "workers": hw["workers"],
"grid_scale": 0.75, "shaders": "standard", "particles_max": 800}
# Standard production: 1080p 24fps
return {"vw": 1920, "vh": 1080, "fps": 24, "crf": 20, "workers": hw["workers"],
"grid_scale": 1.0, "shaders": "full", "particles_max": 1200}
def apply_quality_profile(profile):
"""Set globals from quality profile."""
global VW, VH, FPS, N_WORKERS
VW = profile["vw"]
VH = profile["vh"]
FPS = profile["fps"]
N_WORKERS = profile["workers"]
# Grid sizes scale with resolution
# CRF passed to ffmpeg encoder
# Shader set determines which post-processing is active
```
### CLI Integration
```python
parser = argparse.ArgumentParser()
parser.add_argument("--quality", choices=["draft", "preview", "production", "max", "auto"],
default="auto", help="Render quality preset")
parser.add_argument("--workers", type=int, default=0, help="Override worker count (0=auto)")
parser.add_argument("--resolution", type=str, default="", help="Override resolution e.g. 1280x720")
args = parser.parse_args()
hw = detect_hardware()
if args.workers > 0:
hw["workers"] = args.workers
profile = quality_profile(hw, target_duration, args.quality)
if args.resolution:
w, h = args.resolution.split("x")
profile["vw"], profile["vh"] = int(w), int(h)
apply_quality_profile(profile)
log(f"Hardware: {hw['cpu_count']} cores, {hw['mem_gb']:.1f}GB RAM, {hw['platform']}")
log(f"Render: {profile['vw']}x{profile['vh']} @{profile['fps']}fps, "
f"CRF {profile['crf']}, {profile['workers']} workers")
```
## Performance Budget
Target: 100-200ms per frame (5-10 fps single-threaded, 40-80 fps across 8 workers).
| Component | Time | Notes |
|-----------|------|-------|
| Feature extraction | 1-5ms | Pre-computed for all frames before render |
| Effect function | 2-15ms | Vectorized numpy, avoid Python loops |
| Character render | 80-150ms | **Bottleneck** -- per-cell Python loop |
| Shader pipeline | 5-25ms | Depends on active shaders |
| ffmpeg encode | ~5ms | Amortized by pipe buffering |
## Bitmap Pre-Rasterization
Rasterize every character at init, not per-frame:
```python
# At init time -- done once
for c in all_characters:
img = Image.new("L", (cell_w, cell_h), 0)
ImageDraw.Draw(img).text((0, 0), c, fill=255, font=font)
bitmaps[c] = np.array(img, dtype=np.float32) / 255.0 # float32 for fast multiply
# At render time -- fast lookup
bitmap = bitmaps[char]
canvas[y:y+ch, x:x+cw] = np.maximum(canvas[y:y+ch, x:x+cw],
(bitmap[:,:,None] * color).astype(np.uint8))
```
Collect all characters from all palettes + overlay text into the init set. Lazy-init for any missed characters.
## Coordinate Array Caching
Pre-compute all grid-relative coordinate arrays at init, not per-frame:
```python
# These are O(rows*cols) and used in every effect
self.rr = np.arange(rows)[:, None] # row indices
self.cc = np.arange(cols)[None, :] # col indices
self.dist = np.sqrt(dx**2 + dy**2) # distance from center
self.angle = np.arctan2(dy, dx) # angle from center
self.dist_n = ... # normalized distance
```
## Vectorized Effect Patterns
### Avoid Per-Cell Python Loops in Effects
The render loop (compositing bitmaps) is unavoidably per-cell. But effect functions must be fully vectorized numpy -- never iterate over rows/cols in Python.
Bad (O(rows*cols) Python loop):
```python
for r in range(rows):
for c in range(cols):
val[r, c] = math.sin(c * 0.1 + t) * math.cos(r * 0.1 - t)
```
Good (vectorized):
```python
val = np.sin(g.cc * 0.1 + t) * np.cos(g.rr * 0.1 - t)
```
### Vectorized Matrix Rain
The naive per-column per-trail-pixel loop is the second biggest bottleneck after the render loop. Use numpy fancy indexing:
```python
# Instead of nested Python loops over columns and trail pixels:
# Build row index arrays for all active trail pixels at once
all_rows = []
all_cols = []
all_fades = []
for c in range(cols):
head = int(state["ry"][c])
trail_len = state["rln"][c]
for i in range(trail_len):
row = head - i
if 0 <= row < rows:
all_rows.append(row)
all_cols.append(c)
all_fades.append(1.0 - i / trail_len)
# Vectorized assignment
ar = np.array(all_rows)
ac = np.array(all_cols)
af = np.array(all_fades, dtype=np.float32)
# Assign chars and colors in bulk using fancy indexing
ch[ar, ac] = ... # vectorized char assignment
co[ar, ac, 1] = (af * bri * 255).astype(np.uint8) # green channel
```
### Vectorized Fire Columns
Same pattern -- accumulate index arrays, assign in bulk:
```python
fire_val = np.zeros((rows, cols), dtype=np.float32)
for fi in range(n_cols):
fx_c = int((fi * cols / n_cols + np.sin(t * 2 + fi * 0.7) * 3) % cols)
height = int(energy * rows * 0.7)
dy = np.arange(min(height, rows))
fr = rows - 1 - dy
frac = dy / max(height, 1)
# Width spread: base columns wider at bottom
for dx in range(-1, 2): # 3-wide columns
c = fx_c + dx
if 0 <= c < cols:
fire_val[fr, c] = np.maximum(fire_val[fr, c],
(1 - frac * 0.6) * (0.5 + rms * 0.5))
# Now map fire_val to chars and colors in one vectorized pass
```
## Bloom Optimization
**Do NOT use `scipy.ndimage.uniform_filter`** -- measured at 424ms/frame.
Use 4x downsample + manual box blur instead -- 84ms/frame (5x faster):
```python
sm = canvas[::4, ::4].astype(np.float32) # 4x downsample
br = np.where(sm > threshold, sm, 0)
for _ in range(3): # 3-pass manual box blur
p = np.pad(br, ((1,1),(1,1),(0,0)), mode='edge')
br = (p[:-2,:-2] + p[:-2,1:-1] + p[:-2,2:] +
p[1:-1,:-2] + p[1:-1,1:-1] + p[1:-1,2:] +
p[2:,:-2] + p[2:,1:-1] + p[2:,2:]) / 9.0
bl = np.repeat(np.repeat(br, 4, axis=0), 4, axis=1)[:H, :W]
```
## Vignette Caching
Distance field is resolution- and strength-dependent, never changes per frame:
```python
_vig_cache = {}
def sh_vignette(canvas, strength):
key = (canvas.shape[0], canvas.shape[1], round(strength, 2))
if key not in _vig_cache:
Y = np.linspace(-1, 1, H)[:, None]
X = np.linspace(-1, 1, W)[None, :]
_vig_cache[key] = np.clip(1.0 - np.sqrt(X**2+Y**2) * strength, 0.15, 1).astype(np.float32)
return np.clip(canvas * _vig_cache[key][:,:,None], 0, 255).astype(np.uint8)
```
Same pattern for CRT barrel distortion (cache remap coordinates).
## Film Grain Optimization
Generate noise at half resolution, tile up:
```python
noise = np.random.randint(-amt, amt+1, (H//2, W//2, 1), dtype=np.int16)
noise = np.repeat(np.repeat(noise, 2, axis=0), 2, axis=1)[:H, :W]
```
2x blocky grain looks like film grain and costs 1/4 the random generation.
## Parallel Rendering
### Worker Architecture
```python
hw = detect_hardware()
N_WORKERS = hw["workers"]
# Batch splitting (for non-clip architectures)
batch_size = (n_frames + N_WORKERS - 1) // N_WORKERS
batches = [(i, i*batch_size, min((i+1)*batch_size, n_frames), features, seg_path) ...]
with multiprocessing.Pool(N_WORKERS) as pool:
segments = pool.starmap(render_batch, batches)
```
### Per-Clip Parallelism (Preferred for Segmented Videos)
```python
from concurrent.futures import ProcessPoolExecutor, as_completed
with ProcessPoolExecutor(max_workers=N_WORKERS) as pool:
futures = {pool.submit(render_clip, seg, features, path): seg["id"]
for seg, path in clip_args}
for fut in as_completed(futures):
clip_id = futures[fut]
try:
fut.result()
log(f" {clip_id} done")
except Exception as e:
log(f" {clip_id} FAILED: {e}")
```
### Worker Isolation
Each worker:
- Creates its own `Renderer` instance (with full grid + bitmap init)
- Opens its own ffmpeg subprocess
- Has independent random seed (`random.seed(batch_id * 10000)`)
- Writes to its own segment file and stderr log
### ffmpeg Pipe Safety
**CRITICAL**: Never `stderr=subprocess.PIPE` with long-running ffmpeg. The stderr buffer fills at ~64KB and deadlocks:
```python
# WRONG -- will deadlock
pipe = subprocess.Popen(cmd, stdin=subprocess.PIPE, stderr=subprocess.PIPE)
# RIGHT -- stderr to file
stderr_fh = open(err_path, "w")
pipe = subprocess.Popen(cmd, stdin=subprocess.PIPE, stdout=subprocess.DEVNULL, stderr=stderr_fh)
# ... write all frames ...
pipe.stdin.close()
pipe.wait()
stderr_fh.close()
```
### Concatenation
```python
with open(concat_file, "w") as cf:
for seg in segments:
cf.write(f"file '{seg}'\n")
cmd = ["ffmpeg", "-y", "-f", "concat", "-safe", "0", "-i", concat_file]
if audio_path:
cmd += ["-i", audio_path, "-c:v", "copy", "-c:a", "aac", "-b:a", "192k", "-shortest"]
else:
cmd += ["-c:v", "copy"]
cmd.append(output_path)
subprocess.run(cmd, capture_output=True, check=True)
```
## Particle System Performance
Cap particle counts based on quality profile:
| System | Low | Standard | High |
|--------|-----|----------|------|
| Explosion | 300 | 1000 | 2500 |
| Embers | 500 | 1500 | 3000 |
| Starfield | 300 | 800 | 1500 |
| Dissolve | 200 | 600 | 1200 |
Cull by truncating lists:
```python
MAX_PARTICLES = profile.get("particles_max", 1200)
if len(S["px"]) > MAX_PARTICLES:
for k in ("px", "py", "vx", "vy", "life", "char"):
S[k] = S[k][-MAX_PARTICLES:] # keep newest
```
## Memory Management
- Feature arrays: pre-computed for all frames, shared across workers via fork semantics (COW)
- Canvas: allocated once per worker, reused (`np.zeros(...)`)
- Character arrays: allocated per frame (cheap -- rows*cols U1 strings)
- Bitmap cache: ~500KB per grid size, initialized once per worker
Total memory per worker: ~50-150MB. Total: ~400-800MB for 8 workers.
For low-memory systems (< 4GB), reduce worker count and use smaller grids.
## Brightness Verification
After render, spot-check brightness at sample timestamps:
```python
for t in [2, 30, 60, 120, 180]:
cmd = ["ffmpeg", "-ss", str(t), "-i", output_path,
"-frames:v", "1", "-f", "rawvideo", "-pix_fmt", "rgb24", "-"]
r = subprocess.run(cmd, capture_output=True)
arr = np.frombuffer(r.stdout, dtype=np.uint8)
print(f"t={t}s mean={arr.mean():.1f} max={arr.max()}")
```
Target: mean > 5 for quiet sections, mean > 15 for active sections. If consistently below, increase brightness floor in effects and/or global boost multiplier.
## Render Time Estimates
Scale with hardware. Baseline: 1080p, 24fps, ~180ms/frame/worker.
| Duration | Frames | 4 workers | 8 workers | 16 workers |
|----------|--------|-----------|-----------|------------|
| 30s | 720 | ~3 min | ~2 min | ~1 min |
| 2 min | 2,880 | ~13 min | ~7 min | ~4 min |
| 3.5 min | 5,040 | ~23 min | ~12 min | ~6 min |
| 5 min | 7,200 | ~33 min | ~17 min | ~9 min |
| 10 min | 14,400 | ~65 min | ~33 min | ~17 min |
At 720p: multiply times by ~0.5. At 4K: multiply by ~4.
Heavier effects (many particles, dense grids, extra shader passes) add ~20-50%.

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# Scene System Reference
Scenes are the top-level creative unit. Each scene is a time-bounded segment with its own effect function, shader chain, feedback configuration, and tone-mapping gamma.
## Scene Protocol (v2)
### Function Signature
```python
def fx_scene_name(r, f, t, S) -> canvas:
"""
Args:
r: Renderer instance — access multiple grids via r.get_grid("sm")
f: dict of audio/video features, all values normalized to [0, 1]
t: time in seconds (global, not local to scene)
S: dict for persistent state (particles, rain columns, etc.)
Returns:
canvas: numpy uint8 array, shape (VH, VW, 3) — full pixel frame
"""
```
This replaces the v1 protocol where scenes returned `(chars, colors)` tuples. The v2 protocol gives scenes full control over multi-grid rendering and pixel-level composition internally.
### The Renderer Class
```python
class Renderer:
def __init__(self):
self.grids = {} # lazy-initialized grid cache
self.g = None # "active" grid (for backward compat)
self.S = {} # persistent state dict
def get_grid(self, key):
"""Get or create a GridLayer by size key."""
if key not in self.grids:
sizes = {"xs": 8, "sm": 10, "md": 16, "lg": 20, "xl": 24, "xxl": 40}
self.grids[key] = GridLayer(FONT_PATH, sizes[key])
return self.grids[key]
def set_grid(self, key):
"""Set active grid (legacy). Prefer get_grid() for multi-grid scenes."""
self.g = self.get_grid(key)
return self.g
```
**Key difference from v1**: scenes call `r.get_grid("sm")`, `r.get_grid("lg")`, etc. to access multiple grids. Each grid is lazy-initialized and cached. The `set_grid()` method still works for single-grid scenes.
### Minimal Scene (Single Grid)
```python
def fx_simple_rings(r, f, t, S):
"""Single-grid scene: rings with distance-mapped hue."""
canvas = _render_vf(r, "md",
lambda g, f, t, S: vf_rings(g, f, t, S, n_base=8, spacing_base=3),
hf_distance(0.3, 0.02), PAL_STARS, f, t, S, sat=0.85)
return canvas
```
### Standard Scene (Two Grids + Blend)
```python
def fx_tunnel_ripple(r, f, t, S):
"""Two-grid scene: tunnel depth exclusion-blended with ripple."""
canvas_a = _render_vf(r, "md",
lambda g, f, t, S: vf_tunnel(g, f, t, S, speed=5.0, complexity=10) * 1.3,
hf_distance(0.55, 0.02), PAL_GREEK, f, t, S, sat=0.7)
canvas_b = _render_vf(r, "sm",
lambda g, f, t, S: vf_ripple(g, f, t, S,
sources=[(0.3,0.3), (0.7,0.7), (0.5,0.2)], freq=0.5, damping=0.012) * 1.4,
hf_angle(0.1), PAL_STARS, f, t, S, sat=0.8)
return blend_canvas(canvas_a, canvas_b, "exclusion", 0.8)
```
### Complex Scene (Three Grids + Conditional + Custom Rendering)
```python
def fx_rings_explosion(r, f, t, S):
"""Three-grid scene with particles and conditional kaleidoscope."""
# Layer 1: rings
canvas_a = _render_vf(r, "sm",
lambda g, f, t, S: vf_rings(g, f, t, S, n_base=10, spacing_base=2) * 1.4,
lambda g, f, t, S: (g.angle / (2*np.pi) + t * 0.15) % 1.0,
PAL_STARS, f, t, S, sat=0.9)
# Layer 2: vortex on different grid
canvas_b = _render_vf(r, "md",
lambda g, f, t, S: vf_vortex(g, f, t, S, twist=6.0) * 1.2,
hf_time_cycle(0.15), PAL_BLOCKS, f, t, S, sat=0.8)
result = blend_canvas(canvas_b, canvas_a, "screen", 0.7)
# Layer 3: particles (custom rendering, not _render_vf)
g = r.get_grid("sm")
if "px" not in S:
S["px"], S["py"], S["vx"], S["vy"], S["life"], S["pch"] = (
[], [], [], [], [], [])
if f.get("beat", 0) > 0.5:
chars = list("\u2605\u2736\u2733\u2738\u2726\u2728*+")
for _ in range(int(80 + f.get("rms", 0.3) * 120)):
ang = random.uniform(0, 2 * math.pi)
sp = random.uniform(1, 10) * (0.5 + f.get("sub_r", 0.3) * 2)
S["px"].append(float(g.cols // 2))
S["py"].append(float(g.rows // 2))
S["vx"].append(math.cos(ang) * sp * 2.5)
S["vy"].append(math.sin(ang) * sp)
S["life"].append(1.0)
S["pch"].append(random.choice(chars))
# Update + draw particles
ch_p = np.full((g.rows, g.cols), " ", dtype="U1")
co_p = np.zeros((g.rows, g.cols, 3), dtype=np.uint8)
i = 0
while i < len(S["px"]):
S["px"][i] += S["vx"][i]; S["py"][i] += S["vy"][i]
S["vy"][i] += 0.03; S["life"][i] -= 0.02
if S["life"][i] <= 0:
for k in ("px","py","vx","vy","life","pch"): S[k].pop(i)
else:
pr, pc = int(S["py"][i]), int(S["px"][i])
if 0 <= pr < g.rows and 0 <= pc < g.cols:
ch_p[pr, pc] = S["pch"][i]
co_p[pr, pc] = hsv2rgb_scalar(
0.08 + (1-S["life"][i])*0.15, 0.95, S["life"][i])
i += 1
canvas_p = g.render(ch_p, co_p)
result = blend_canvas(result, canvas_p, "add", 0.8)
# Conditional kaleidoscope on strong beats
if f.get("bdecay", 0) > 0.4:
result = sh_kaleidoscope(result.copy(), folds=6)
return result
```
### Scene with Custom Character Rendering (Matrix Rain)
When you need per-cell control beyond what `_render_vf()` provides:
```python
def fx_matrix_layered(r, f, t, S):
"""Matrix rain blended with tunnel — two grids, screen blend."""
# Layer 1: Matrix rain (custom per-column rendering)
g = r.get_grid("md")
rows, cols = g.rows, g.cols
pal = PAL_KATA
if "ry" not in S or len(S["ry"]) != cols:
S["ry"] = np.random.uniform(-rows, rows, cols).astype(np.float32)
S["rsp"] = np.random.uniform(0.3, 2.0, cols).astype(np.float32)
S["rln"] = np.random.randint(8, 35, cols)
S["rch"] = np.random.randint(1, len(pal), (rows, cols))
speed = 0.6 + f.get("bass", 0.3) * 3
if f.get("beat", 0) > 0.5: speed *= 2.5
S["ry"] += S["rsp"] * speed
ch = np.full((rows, cols), " ", dtype="U1")
co = np.zeros((rows, cols, 3), dtype=np.uint8)
heads = S["ry"].astype(int)
for c in range(cols):
head = heads[c]
for i in range(S["rln"][c]):
row = head - i
if 0 <= row < rows:
fade = 1.0 - i / S["rln"][c]
ch[row, c] = pal[S["rch"][row, c] % len(pal)]
if i == 0:
v = int(min(255, fade * 300))
co[row, c] = (int(v*0.9), v, int(v*0.9))
else:
v = int(fade * 240)
co[row, c] = (int(v*0.1), v, int(v*0.4))
canvas_a = g.render(ch, co)
# Layer 2: Tunnel on sm grid for depth texture
canvas_b = _render_vf(r, "sm",
lambda g, f, t, S: vf_tunnel(g, f, t, S, speed=5.0, complexity=10),
hf_distance(0.3, 0.02), PAL_BLOCKS, f, t, S, sat=0.6)
return blend_canvas(canvas_a, canvas_b, "screen", 0.5)
```
---
## Scene Table
The scene table defines the timeline: which scene plays when, with what configuration.
### Structure
```python
SCENES = [
{
"start": 0.0, # start time in seconds
"end": 3.96, # end time in seconds
"name": "starfield", # identifier (used for clip filenames)
"grid": "sm", # default grid (for render_clip setup)
"fx": fx_starfield, # scene function reference (must be module-level)
"gamma": 0.75, # tonemap gamma override (default 0.75)
"shaders": [ # shader chain (applied after tonemap + feedback)
("bloom", {"thr": 120}),
("vignette", {"s": 0.2}),
("grain", {"amt": 8}),
],
"feedback": None, # feedback buffer config (None = disabled)
# "feedback": {"decay": 0.8, "blend": "screen", "opacity": 0.3,
# "transform": "zoom", "transform_amt": 0.02, "hue_shift": 0.02},
},
{
"start": 3.96,
"end": 6.58,
"name": "matrix_layered",
"grid": "md",
"fx": fx_matrix_layered,
"shaders": [
("crt", {"strength": 0.05}),
("scanlines", {"intensity": 0.12}),
("color_grade", {"tint": (0.7, 1.2, 0.7)}),
("bloom", {"thr": 100}),
],
"feedback": {"decay": 0.5, "blend": "add", "opacity": 0.2},
},
# ... more scenes ...
]
```
### Beat-Synced Scene Cutting
Derive cut points from audio analysis:
```python
# Get beat timestamps
beats = [fi / FPS for fi in range(N_FRAMES) if features["beat"][fi] > 0.5]
# Group beats into phrase boundaries (every 4-8 beats)
cuts = [0.0]
for i in range(0, len(beats), 4): # cut every 4 beats
cuts.append(beats[i])
cuts.append(DURATION)
# Or use the music's structure: silence gaps, energy changes
energy = features["rms"]
# Find timestamps where energy drops significantly -> natural break points
```
### `render_clip()` — The Render Loop
This function renders one scene to a clip file:
```python
def render_clip(seg, features, clip_path):
r = Renderer()
r.set_grid(seg["grid"])
S = r.S
random.seed(hash(seg["id"]) + 42) # deterministic per scene
# Build shader chain from config
chain = ShaderChain()
for shader_name, kwargs in seg.get("shaders", []):
chain.add(shader_name, **kwargs)
# Setup feedback buffer
fb = None
fb_cfg = seg.get("feedback", None)
if fb_cfg:
fb = FeedbackBuffer()
fx_fn = seg["fx"]
# Open ffmpeg pipe
cmd = ["ffmpeg", "-y", "-f", "rawvideo", "-pix_fmt", "rgb24",
"-s", f"{VW}x{VH}", "-r", str(FPS), "-i", "pipe:0",
"-c:v", "libx264", "-preset", "fast", "-crf", "20",
"-pix_fmt", "yuv420p", clip_path]
stderr_fh = open(clip_path.replace(".mp4", ".log"), "w")
pipe = subprocess.Popen(cmd, stdin=subprocess.PIPE,
stdout=subprocess.DEVNULL, stderr=stderr_fh)
for fi in range(seg["frame_start"], seg["frame_end"]):
t = fi / FPS
feat = {k: float(features[k][fi]) for k in features}
# 1. Scene renders canvas
canvas = fx_fn(r, feat, t, S)
# 2. Tonemap normalizes brightness
canvas = tonemap(canvas, gamma=seg.get("gamma", 0.75))
# 3. Feedback adds temporal recursion
if fb and fb_cfg:
canvas = fb.apply(canvas, **{k: fb_cfg[k] for k in fb_cfg})
# 4. Shader chain adds post-processing
canvas = chain.apply(canvas, f=feat, t=t)
pipe.stdin.write(canvas.tobytes())
pipe.stdin.close(); pipe.wait(); stderr_fh.close()
```
### Building Segments from Scene Table
```python
segments = []
for i, scene in enumerate(SCENES):
segments.append({
"id": f"s{i:02d}_{scene['name']}",
"name": scene["name"],
"grid": scene["grid"],
"fx": scene["fx"],
"shaders": scene.get("shaders", []),
"feedback": scene.get("feedback", None),
"gamma": scene.get("gamma", 0.75),
"frame_start": int(scene["start"] * FPS),
"frame_end": int(scene["end"] * FPS),
})
```
### Parallel Rendering
Scenes are independent units dispatched to a process pool:
```python
from concurrent.futures import ProcessPoolExecutor, as_completed
with ProcessPoolExecutor(max_workers=N_WORKERS) as pool:
futures = {
pool.submit(render_clip, seg, features, clip_path): seg["id"]
for seg, clip_path in zip(segments, clip_paths)
}
for fut in as_completed(futures):
try:
fut.result()
except Exception as e:
log(f"ERROR {futures[fut]}: {e}")
```
**Pickling constraint**: `ProcessPoolExecutor` serializes arguments via pickle. Module-level functions can be pickled; lambdas and closures cannot. All `fx_*` scene functions MUST be defined at module level, not as closures or class methods.
### Test-Frame Mode
Render a single frame at a specific timestamp to verify visuals without a full render:
```python
if args.test_frame >= 0:
fi = min(int(args.test_frame * FPS), N_FRAMES - 1)
t = fi / FPS
feat = {k: float(features[k][fi]) for k in features}
scene = next(sc for sc in reversed(SCENES) if t >= sc["start"])
r = Renderer()
r.set_grid(scene["grid"])
canvas = scene["fx"](r, feat, t, r.S)
canvas = tonemap(canvas, gamma=scene.get("gamma", 0.75))
chain = ShaderChain()
for sn, kw in scene.get("shaders", []):
chain.add(sn, **kw)
canvas = chain.apply(canvas, f=feat, t=t)
Image.fromarray(canvas).save(f"test_{args.test_frame:.1f}s.png")
print(f"Mean brightness: {canvas.astype(float).mean():.1f}")
```
CLI: `python reel.py --test-frame 10.0`
---
## Scene Design Checklist
For each scene:
1. **Choose 2-3 grid sizes** — different scales create interference
2. **Choose different value fields** per layer — don't use the same effect on every grid
3. **Choose different hue fields** per layer — or at minimum different hue offsets
4. **Choose different palettes** per layer — mixing PAL_RUNE with PAL_BLOCKS looks different from PAL_RUNE with PAL_DENSE
5. **Choose a blend mode** that matches the energy — screen for bright, difference for psychedelic, exclusion for subtle
6. **Add conditional effects** on beat — kaleidoscope, mirror, glitch
7. **Configure feedback** for trailing/recursive looks — or None for clean cuts
8. **Set gamma** if using destructive shaders (solarize, posterize)
9. **Test with --test-frame** at the scene's midpoint before full render

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# Troubleshooting Reference
Common bugs, gotchas, and platform-specific issues encountered during ASCII video development.
## NumPy Broadcasting
### The `broadcast_to().copy()` Trap
Hue field generators often return arrays that are broadcast views — they have shape `(1, cols)` or `(rows, 1)` that numpy broadcasts to `(rows, cols)`. These views are **read-only**. If any downstream code tries to modify them in-place (e.g., `h %= 1.0`), numpy raises:
```
ValueError: output array is read-only
```
**Fix**: Always `.copy()` after `broadcast_to()`:
```python
h = np.broadcast_to(h, (g.rows, g.cols)).copy()
```
This is especially important in `_render_vf()` where hue arrays flow through `hsv2rgb()`.
### The `+=` vs `+` Trap
Broadcasting also fails with in-place operators when operand shapes don't match exactly:
```python
# FAILS if result is (rows,1) and operand is (rows, cols)
val += np.sin(g.cc * 0.02 + t * 0.3) * 0.5
# WORKS — creates a new array
val = val + np.sin(g.cc * 0.02 + t * 0.3) * 0.5
```
The `vf_plasma()` function had this bug. Use `+` instead of `+=` when mixing different-shaped arrays.
### Shape Mismatch in `hsv2rgb()`
`hsv2rgb(h, s, v)` requires all three arrays to have identical shapes. If `h` is `(1, cols)` and `s` is `(rows, cols)`, the function crashes or produces wrong output.
**Fix**: Ensure all inputs are broadcast and copied to `(rows, cols)` before calling.
---
## Blend Mode Pitfalls
### Overlay Crushes Dark Inputs
`overlay(a, b) = 2*a*b` when `a < 0.5`. Two values of 0.12 produce `2 * 0.12 * 0.12 = 0.03`. The result is darker than either input.
**Impact**: If both layers are dark (which ASCII art usually is), overlay produces near-black output.
**Fix**: Use `screen` for dark source material. Screen always brightens: `1 - (1-a)*(1-b)`.
### Colordodge Division by Zero
`colordodge(a, b) = a / (1 - b)`. When `b = 1.0` (pure white pixels), this divides by zero.
**Fix**: Add epsilon: `a / (1 - b + 1e-6)`. The implementation in `BLEND_MODES` should include this.
### Colorburn Division by Zero
`colorburn(a, b) = 1 - (1-a) / b`. When `b = 0` (pure black pixels), this divides by zero.
**Fix**: Add epsilon: `1 - (1-a) / (b + 1e-6)`.
### Multiply Always Darkens
`multiply(a, b) = a * b`. Since both operands are [0,1], the result is always <= min(a,b). Never use multiply as a feedback blend mode — the frame goes black within a few frames.
**Fix**: Use `screen` for feedback, or `add` with low opacity.
---
## Multiprocessing
### Pickling Constraints
`ProcessPoolExecutor` serializes function arguments via pickle. This constrains what you can pass to workers:
| Can Pickle | Cannot Pickle |
|-----------|---------------|
| Module-level functions (`def fx_foo():`) | Lambdas (`lambda x: x + 1`) |
| Dicts, lists, numpy arrays | Closures (functions defined inside functions) |
| Class instances (with `__reduce__`) | Instance methods |
| Strings, numbers | File handles, sockets |
**Impact**: All scene functions referenced in the SCENES table must be defined at module level with `def`. If you use a lambda or closure, you get:
```
_pickle.PicklingError: Can't pickle <function <lambda> at 0x...>
```
**Fix**: Define all scene functions at module top level. Lambdas used inside `_render_vf()` as val_fn/hue_fn are fine because they execute within the worker process — they're not pickled across process boundaries.
### macOS spawn vs Linux fork
On macOS, `multiprocessing` defaults to `spawn` (full serialization). On Linux, it defaults to `fork` (copy-on-write). This means:
- **macOS**: Feature arrays are serialized per worker (~57KB for 30s video, but scales with duration). Each worker re-imports the entire module.
- **Linux**: Feature arrays are shared via COW. Workers inherit the parent's memory.
**Impact**: On macOS, module-level code (like `detect_hardware()`) runs in every worker process. If it has side effects (e.g., subprocess calls), those happen N+1 times.
### Per-Worker State Isolation
Each worker creates its own:
- `Renderer` instance (with fresh grid cache)
- `FeedbackBuffer` (feedback doesn't cross scene boundaries)
- Random seed (`random.seed(hash(seg_id) + 42)`)
This means:
- Particle state doesn't carry between scenes (expected)
- Feedback trails reset at scene cuts (expected)
- `np.random` state is NOT seeded by `random.seed()` — they use separate RNGs
**Fix for deterministic noise**: Use `np.random.RandomState(seed)` explicitly:
```python
rng = np.random.RandomState(hash(seg_id) + 42)
noise = rng.random((rows, cols))
```
---
## Brightness Issues
### Dark Scenes After Tonemap
If a scene is still dark after tonemap, check:
1. **Gamma too high**: Lower gamma (0.5-0.6) for scenes with destructive post-processing
2. **Shader destroying brightness**: Solarize, posterize, or contrast adjustments in the shader chain can undo tonemap's work. Move destructive shaders earlier in the chain, or increase gamma to compensate.
3. **Feedback with multiply**: Multiply feedback darkens every frame. Switch to screen or add.
4. **Overlay blend in scene**: If the scene function uses `blend_canvas(..., "overlay", ...)` with dark layers, switch to screen.
### Diagnostic: Test-Frame Brightness
```bash
python reel.py --test-frame 10.0
# Output: Mean brightness: 44.3, max: 255
```
If mean < 20, the scene needs attention. Common fixes:
- Lower gamma in the SCENES entry
- Change internal blend modes from overlay/multiply to screen/add
- Increase value field multipliers (e.g., `vf_plasma(...) * 1.5`)
- Check that the shader chain doesn't have an aggressive solarize or threshold
### v1 Brightness Pattern (Deprecated)
The old pattern used a linear multiplier:
```python
# OLD — don't use
canvas = np.clip(canvas.astype(np.float32) * 2.0, 0, 255).astype(np.uint8)
```
This fails because:
- Dark scenes (mean 8): `8 * 2.0 = 16` — still dark
- Bright scenes (mean 130): `130 * 2.0 = 255` — clipped, lost detail
Use `tonemap()` instead. See `composition.md` § Adaptive Tone Mapping.
---
## ffmpeg Issues
### Pipe Deadlock
The #1 production bug. If you use `stderr=subprocess.PIPE`:
```python
# DEADLOCK — stderr buffer fills at 64KB, blocks ffmpeg, blocks your writes
pipe = subprocess.Popen(cmd, stdin=subprocess.PIPE, stderr=subprocess.PIPE)
```
**Fix**: Always redirect stderr to a file:
```python
stderr_fh = open(err_path, "w")
pipe = subprocess.Popen(cmd, stdin=subprocess.PIPE,
stdout=subprocess.DEVNULL, stderr=stderr_fh)
```
### Frame Count Mismatch
If the number of frames written to the pipe doesn't match what ffmpeg expects (based on `-r` and duration), the output may have:
- Missing frames at the end
- Incorrect duration
- Audio-video desync
**Fix**: Calculate frame count explicitly: `n_frames = int(duration * FPS)`. Don't use `range(int(start*FPS), int(end*FPS))` without verifying the total matches.
### Concat Fails with "unsafe file name"
```
[concat @ ...] Unsafe file name
```
**Fix**: Always use `-safe 0`:
```python
["ffmpeg", "-f", "concat", "-safe", "0", "-i", concat_path, ...]
```
---
## Font Issues
### Cell Height (macOS Pillow)
`textbbox()` and `getbbox()` return incorrect heights on some macOS Pillow versions. Use `getmetrics()`:
```python
ascent, descent = font.getmetrics()
cell_height = ascent + descent # correct
# NOT: font.getbbox("M")[3] # wrong on some versions
```
### Missing Unicode Glyphs
Not all fonts render all Unicode characters. If a palette character isn't in the font, the glyph renders as a blank or tofu box, appearing as a dark hole in the output.
**Fix**: Validate at init:
```python
all_chars = set()
for pal in [PAL_DEFAULT, PAL_DENSE, PAL_RUNE, ...]:
all_chars.update(pal)
valid_chars = set()
for c in all_chars:
if c == " ":
valid_chars.add(c)
continue
img = Image.new("L", (20, 20), 0)
ImageDraw.Draw(img).text((0, 0), c, fill=255, font=font)
if np.array(img).max() > 0:
valid_chars.add(c)
else:
log(f"WARNING: '{c}' (U+{ord(c):04X}) missing from font")
```
### Platform Font Paths
| Platform | Common Paths |
|----------|-------------|
| macOS | `/System/Library/Fonts/Menlo.ttc`, `/System/Library/Fonts/Monaco.ttf` |
| Linux | `/usr/share/fonts/truetype/dejavu/DejaVuSansMono.ttf` |
| Windows | `C:\Windows\Fonts\consola.ttf` (Consolas) |
Always probe multiple paths and fall back gracefully. See `architecture.md` § Font Selection.
---
## Performance
### Slow Shaders
Some shaders use Python loops and are very slow at 1080p:
| Shader | Issue | Fix |
|--------|-------|-----|
| `wave_distort` | Per-row Python loop | Use vectorized fancy indexing |
| `halftone` | Triple-nested loop | Vectorize with block reduction |
| `matrix rain` | Per-column per-trail loop | Accumulate index arrays, bulk assign |
### Render Time Scaling
If render is taking much longer than expected:
1. Check grid count — each extra grid adds ~100-150ms/frame for init
2. Check particle count — cap at quality-appropriate limits
3. Check shader count — each shader adds 2-25ms
4. Check for accidental Python loops in effects (should be numpy only)
---
## Common Mistakes
### Using `r.S` vs the `S` Parameter
The v2 scene protocol passes `S` (the state dict) as an explicit parameter. But `S` IS `r.S` — they're the same object. Both work:
```python
def fx_scene(r, f, t, S):
S["counter"] = S.get("counter", 0) + 1 # via parameter (preferred)
r.S["counter"] = r.S.get("counter", 0) + 1 # via renderer (also works)
```
Use the `S` parameter for clarity. The explicit parameter makes it obvious that the function has persistent state.
### Forgetting to Handle Empty Feature Values
Audio features default to 0.0 if the audio is silent. Use `.get()` with sensible defaults:
```python
energy = f.get("bass", 0.3) # default to 0.3, not 0
```
If you default to 0, effects go blank during silence.
### Writing New Files Instead of Editing Existing State
A common bug in particle systems: creating new arrays every frame instead of updating persistent state.
```python
# WRONG — particles reset every frame
S["px"] = []
for _ in range(100):
S["px"].append(random.random())
# RIGHT — only initialize once, update each frame
if "px" not in S:
S["px"] = []
# ... emit new particles based on beats
# ... update existing particles
```
### Not Clipping Value Fields
Value fields should be [0, 1]. If they exceed this range, `val2char()` produces index errors:
```python
# WRONG — vf_plasma() * 1.5 can exceed 1.0
val = vf_plasma(g, f, t, S) * 1.5
# RIGHT — clip after scaling
val = np.clip(vf_plasma(g, f, t, S) * 1.5, 0, 1)
```
The `_render_vf()` helper clips automatically, but if you're building custom scenes, clip explicitly.