--- name: Shader Generator slug: shader-generator category: AI Engineering description: Generates custom WebGL shaders for video effects, transitions, masks, and color grading. First tries built-in effects and assets before generating custom shaders via a beta AI generation pipeline. github: "https://github.com/0xsline/OpenChatCut/tree/main/src/agent/skills/shader-gen" language: TypeScript stars: 837 forks: 109 install: "git clone https://github.com/0xsline/OpenChatCut" added: 2026-08-06T07:41:48.759Z last_synced: 2026-08-06T07:41:48.759Z canonical_url: "https://dirskills.com/skills/shader-generator" --- # Shader Generator Generates custom WebGL shaders for video effects, transitions, masks, and color grading. First tries built-in effects and assets before generating custom shaders via a beta AI generation pipeline. **Install:** `git clone https://github.com/0xsline/OpenChatCut` ## README # Shader Generator Submit-only: creates a backend generation job, returns `jobId`. Use the `track_progress` tool for job lifecycle after submission. **Always use `generate.ts` for new shaders.** Manual authoring is only for editing existing asset code — never as a fallback when generation fails. ## Catalog-first rule — try existing assets before generation Before generating a shader, call `browse_library` unless the user names an exact asset id that is already visible in `read_project`. `browse_library` is the source of truth for built-in effects, built-in transitions, and project effect/transition assets. Built-ins are stable global asset ids, not per-project DB assets, so they may not appear in `read_project` asset lists. Apply catalog entries with `edit_item`, do **not** call `submit_shader`. Good catalog searches: ```text browse_library(query: "zoom") browse_library(category: "transitions", query: "dissolve") browse_library(category: "audio-fx") ``` Generate only when no catalog entry matches the user's intent closely enough. ### `builtin:zoom` is track-bound only — DO NOT use item-bound The default effect mode is `"item-bound"` (attach to a single item via `targetItemId`). **`builtin:zoom` does NOT render in item-bound mode** — the renderer reads zoom data exclusively from track-bound effect items. An item-bound zoom inserts into the DB silently but shows nothing in preview. Use `mode: "track-bound"` with `trackId` + `trackBoundFrom` + `trackBoundDurationInFrames`. These three fields are required. ```text # Zoom on the entire video clip edit_item(json: '{"adds":[{"type":"effect","assetId":"builtin:zoom","mode":"track-bound","trackId":"","trackBoundFrom":,"trackBoundDurationInFrames":,"propertyOverrides":{"magnification":1.5,"shape":"hold"}}]}') # Zoom on a sub-range of the clip (e.g. frames 90–150 only, a punch zoom on a beat) edit_item(json: '{"adds":[{"type":"effect","assetId":"builtin:zoom","mode":"track-bound","trackId":"","trackBoundFrom":90,"trackBoundDurationInFrames":60,"propertyOverrides":{"magnification":2,"shape":"punch"}}]}') ``` Get `trackId` / `fromFrame` / `durationInFrames` from `read_project` (each video/image item lists its trackId and timeline-frame range). | Key | Type | Range / values | Default | Notes | | --------------- | ------ | ------------------------------------------ | ------- | ---------------------------------------------- | | `magnification` | number | 1–4 | `1.5` | Zoom factor; 1 = no zoom, 2 = 2× in | | `focalPointX` | number | 0–1 | `0.5` | Horizontal focal point (0 = left, 1 = right) | | `focalPointY` | number | 0–1 | `0.5` | Vertical focal point (0 = top, 1 = bottom) | | `shape` | select | `punch` / `hold` / `slow-push` / `instant` | `hold` | Animation curve | | `focalMode` | select | `auto` / `manual` | `auto` | `auto` picks subject; `manual` uses focalPoint | | `easeInFrames` | number | 0–60 | `8` | Frames to ramp in | | `easeOutFrames` | number | 0–60 | `8` | Frames to ramp out | Omit `propertyOverrides` entirely for default zoom. Send only the keys you want to change — patch semantics. ### Track-bound vs item-bound — the broader rule Effect items in the schema have two modes: - **`item-bound`** (default): `targetItemId` only. Effect covers the whole target item's playback. Works for shader effects, LUTs, color grades, blurs. - **`track-bound`**: `trackId` + `trackBoundFrom` + `trackBoundDurationInFrames`. Effect covers a timeline range on a track, independent of any item. Required for `builtin:zoom`; also valid for any shader effect when you want it to cover a specific timeline range (e.g. a transition-like color shift across the boundary of two clips). Default to item-bound for shader effects. Use track-bound when (a) the asset requires it (zoom), or (b) the effect should cover a timeline range that doesn't match a single item. ### Built-in LUT properties ```text edit_item(json: '{"adds":[{"type":"effect","targetItemId":"","assetId":"builtin:slog3-s709","propertyOverrides":{"intensity":1}}]}') ``` | Key | Type | Range | Default | Notes | | ----------- | ------ | ----- | ------- | ------------------------------ | | `intensity` | number | 0–1 | `1` | LUT strength; 1 = full applied | To swap: delete the effect and re-add with a different `assetId`. To remove: delete the effect item. These are separate from user-uploaded `.cube` LUT assets (see "Applying an Existing LUT Asset" below) — those use a different code path with `assetId:"lut"`. ## Beta Status Gate New shader generation is beta. Before generating, warn the user and wait for explicit confirmation. Use the user's language. Chinese: "新的特效/转场生成目前还是 beta 阶段，可能会有不稳定的问题。如果你坚持要做，我可以帮你实现。" Skip if user already acknowledged in the same request. ## Supported Targets Effects and transitions apply to `video`, `image`, and `gif` items. ## Type Routing Before generating anything, check two non-generation paths first: 1. **Catalog entry** — use `browse_library` for built-in and project effects/transitions. 2. **User-uploaded `.cube` LUT asset** that already exists in the project library — separate code path, see "Applying an Existing LUT Asset" below. The asset shows up in `read_project` with `type: lut`. | User wants | `--type` | | -------------------------------------------------------------------- | ------------ | | Video appearance (color, blur, glow, grain, distortion) | `effect` | | Color grade / look (teal-orange, cinematic, vintage, LUT-style) | `effect` | | Visibility control (mask, reveal, wipe, shape cutout, gradient fade) | `effect` | | Blend between clips (crossfade, dissolve, slide, 3D cube/page flip) | `transition` | "LUT-style" in the table means **generating a fresh GLSL color grade that resembles a LUT** — only when the user wants something new. If they want to apply a `.cube` file already in the library, don't generate; bind the existing asset instead. No separate LUT or mask generator for the generation path — those are all `effect`. ## Applying an Existing LUT Asset `.cube` files uploaded by the user become `lut` assets. Applying one to a clip is **not** generation — it's a single `edit_item` call that attaches an effect item whose `assetId` is the literal string `"lut"` and whose `propertyOverrides.lut` binds the real LUT asset id. (Legacy contract; the unified LUT API binds the LUT effect asset id directly — see `edit_item` description.) ```text edit_item(json: '{"adds":[{"type":"effect","targetItemId":"","assetId":"lut","propertyOverrides":{"intensity":1,"lut":{"assetId":"","assetType":"lut","type":"asset"}}}]}') ``` Key points: - `assetId` is the literal string `"lut"`, not the LUT asset's id. The real LUT asset id goes inside `propertyOverrides.lut.assetId`. - `intensity` is 0–1; default 1 (full strength). - `targetItemType` defaults to `video`; also supports `image`, `gif`. - To swap a LUT on an existing effect: update `propertyOverrides.lut.assetId` to the new LUT asset id. - To remove: delete the effect item. Do not call `generate.ts` for this path. Do not pass a real LUT asset id as `assetId` — the editor checks `assetId === "lut"` to route into the LUT renderer; passing a UUID silently renders nothing. ## Usage Before calling `submit_shader`, restate the user's intent in one concrete sentence, then proceed immediately. After `track_progress` returns, state what was produced in one line — do NOT ask "要保留还是重新生成". ```ts submit_shader({ type: "effect", prompt: "Chromatic aberration with RGB split", name: "Chromatic Aberration", }); submit_shader({ type: "transition", prompt: "Smooth crossfade with soft edge", name: "Crossfade", }); submit_shader({ type: "effect", prompt: "Cinematic teal-orange color grade", }); submit_shader({ type: "effect", prompt: "Stronger version", referenceAssetIds: ["effect_asset_id"], }); ``` ## Strategy - Submit, then stop. Tell user the job was created. - Use the `track_progress` tool for status/wait after submission. - Generation always produces a library asset — never refuse because the timeline isn't ready. - **Apply is separate and optional.** Only apply when user explicitly asks ("加到视频", "apply", "用到第一段"). When ambiguous, default to library-only. ## Editing Existing Properties Any time you're about to edit shader `asset.properties`, applied effect/transition `item.propertyOverrides`, or promote a hardcoded shader value, read [`references/property-changes.md`](references/property-changes.md) first. It reinforces that shader `properties` is an array, but the allowed shader property types are only `number`, `boolean`, `color`, `select`, and `vec2`. Motion Graphic properties are also arrays, but use a different type set. ## Parameters | Param | Description | Default | | ------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------- | | `type` | `"effect"` or `"transition"` (req'd) | — | | `prompt` | Description of the shader (req'd) | — | | `name` | Asset name shown in library | — | | `referenceAssetIds` | Asset ids. Image id → model LOOKS AT it for visual inspiration. Effect/transition id → reuse its code as style anchor (≤1 per submit, kind must match `type`). | — | ## Output Returns `{ success, job: { jobId, status }, manage: { status, wait, watch } }`. ## Applying to Timeline Only when user explicitly requests. Call `read_project` first for fresh timeline state. ### Effect ```text edit_item(json: '{"adds":[{"type":"effect","targetItemId":"","assetId":"","enabled":true,"propertyOverrides":{}}]}') ``` ### Transition Requires two adjacent same-track endpoints. `edit_item` validates live seam feasibility and refuses durations that would require freeze frames or overlapping neighboring transitions. If the add fails, retry with the suggested `durationInFrames`, trim the clips to expose handles, delete/shorten neighboring transitions, or keep a hard cut. ```text edit_item(json: '{"adds":[{"type":"transition","assetId":"","outgoingItemId":"","incomingItemId":"","durationInFrames":30}]}') ``` ## Validation & Verification ### Backend Validation When generating via `generate.ts`, the backend handles validation automatically (transpile, AST security, class structure, retry on failure). ### Manual Code Verification **NEVER write shader code from scratch.** Always use `generate.ts` for new shaders. This section is ONLY for modifying existing shader code that was already generated. When writing shader code manually, read `${CLAUDE_SKILL_DIR}/references/design-principles.md` first. If the change touches editable properties, also read `${CLAUDE_SKILL_DIR}/references/property-changes.md`. Typical workflow: 1. `read_project` with the shader `assetId` and `code: true` — read the current source. 2. Edit the source in your own context. 3. `edit_asset` with `action=update`, the same `assetId`, and the full replacement source inline in `json.code`. Validation runs automatically on update — if code is invalid, the update is rejected with error details.