add-effect

# Add a new `@remotion/effects` effect Use this skill when adding a new effect to `@remotion/effects`. ## 1. Pick the effect shape - Prefer the WebGL2 backend for new effects. Use 2D only when WebGL cannot express the effect. - Use a single file at `packages/effects/src/<effect-name>.ts` for simple effects. - Use a folder at `packages/effects/src/<effect-name>/` plus a top-level re-export file when the effect needs multiple shaders, runtime helpers, or multiple files. - Follow naming already used by the package: - File/subpath: kebab-case (`chromatic-aberration`) - Function: camelCase (`chromaticAberration`) - Type: PascalCase params (`ChromaticAberrationParams`) - Effect type string: `remotion/<kebab-case-name>` ## 2. Implement the effect In the effect file: - Import `SequenceSchema` and `Internals` from `remotion`. - Use `const {createEffect, createWebGL2ContextError} = Internals;`. - Define defaults as `const` values. - Define a schema with `satisfies SequenceSchema`; these fields appear in Studio visual editing. - Export the params type. - Resolve defaults in a `resolve()` helper. - Validate params using helpers from: - `packages/effects/src/validate-effect-param.ts` - `packages/effects/src/color-utils.ts` - Throw `createWebGL2ContextError('<effect name> effect')` if WebGL2 cannot be acquired. - Set `documentationLink` to `https://www.remotion.dev/docs/effects/<slug>`. - Include every resolved parameter in `calculateKey()`. For WebGL2 effects, use this general structure: ```ts import type {SequenceSchema} from 'remotion'; import {Internals} from 'remotion'; import {assertOptionalFiniteNumber, validateUnitInterval} from './color-utils.js'; import {assertEffectParamsObject} from './validate-effect-param.js'; const {createEffect, createWebGL2ContextError} = Internals; const DEFAULT_AMOUNT = 1 as const; const myEffectSchema = { amount: { type: 'number', min: 0, max: 1, step: 0.01, default: DEFAULT_AMOUNT, description: 'Amount', }, } as const satisfies SequenceSchema; export type MyEffectParams = { readonly amount?: number; }; type MyEffectResolved = { amount: number; }; const resolve = (p: MyEffectParams): MyEffectResolved => ({ amount: p.amount ?? DEFAULT_AMOUNT, }); const validateMyEffectParams = (params: MyEffectParams): void => { assertEffectParamsObject(params, 'My effect'); assertOptionalFiniteNumber(params.amount, 'amount'); validateUnitInterval(params.amount ?? DEFAULT_AMOUNT, 'amount'); }; type MyEffectState = { readonly gl: WebGL2RenderingContext; readonly program: WebGLProgram; readonly vao: WebGLVertexArrayObject; readonly vbo: WebGLBuffer; readonly texture: WebGLTexture; readonly uSource: WebGLUniformLocation | null; readonly uAmount: WebGLUniformLocation | null; }; const VERTEX_SHADER = /* glsl */ `#version 300 es in vec2 aPos; in vec2 aUv; out vec2 vUv; void main() { vUv = aUv; gl_Position = vec4(aPos, 0.0, 1.0); } `; const FRAGMENT_SHADER = /* glsl */ `#version 300 es precision highp float; in vec2 vUv; out vec4 fragColor; uniform sampler2D uSource; uniform float uAmount; void main() { vec4 color = texture(uSource, vUv); fragColor = vec4(color.rgb * uAmount, color.a); } `; // Follow existing helpers in halftone.ts or a runtime file for shader // compilation, program linking, fullscreen-quad setup, and texture setup. export const myEffect = createEffect<MyEffectParams, MyEffectState>({ type: 'remotion/my-effect', label: 'My Effect', documentationLink: 'https://www.remotion.dev/docs/effects/my-effect', backend: 'webgl2', calculateKey: (params) => { const r = resolve(params); return `my-effect-${r.amount}`; }, setup: (target) => { const gl = target.getContext('webgl2', { premultipliedAlpha: true, alpha: true, preserveDrawingBuffer: true, }); if (!gl) { throw createWebGL2ContextError('my effect effect'); } gl.pixelStorei(gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, true); return createMyEffectState(gl, VERTEX_SHADER, FRAGMENT_SHADER); }, apply: ({source, width, height, params, state, flipSourceY}) => { const r = resolve(params); state.gl.viewport(0, 0, width, height); state.gl.bindFramebuffer(state.gl.FRAMEBUFFER, null); state.gl.activeTexture(state.gl.TEXTURE0); state.gl.bindTexture(state.gl.TEXTURE_2D, state.texture); state.gl.pixelStorei(state.gl.UNPACK_FLIP_Y_WEBGL, flipSourceY); state.gl.texImage2D( state.gl.TEXTURE_2D, 0, state.gl.RGBA, state.gl.RGBA, state.gl.UNSIGNED_BYTE, source as TexImageSource, ); state.gl.useProgram(state.program); if (state.uSource) state.gl.uniform1i(state.uSource, 0); if (state.uAmount) state.gl.uniform1f(state.uAmount, r.amount); state.gl.bindVertexArray(state.vao); state.gl.drawArrays(state.gl.TRIANGLE_STRIP, 0, 4); }, cleanup: ({gl, program, vao, vbo, texture}) => { gl.deleteTexture(texture); gl.deleteBuffer(vbo); gl.deleteProgram(program); gl.deleteVertexArray(vao); }, schema: myEffectSchema, validateParams: validateMyEffectParams, }); ``` Look at existing WebGL2 effects such as `halftone.ts`, `blur/blur-runtime.ts`, `chromatic-aberration/chromatic-aberration-runtime.ts`, and `wave/wave-runtime.ts` before adding new helpers. In the template above, `createMyEffectState()` stands for the shader compilation, program linking, fullscreen-quad, texture, and uniform-location setup used by those files. ## 3. Register package entry points Update: - `packages/effects/bundle.ts` — add the new `src/<effect-name>.ts` entrypoint. - `packages/effects/package.json`: - Add `exports["./<effect-name>"]`. - Add the `typesVersions` entry. If using a folder implementation, add a top-level file that re-exports from the folder: ```ts export {myEffect, type MyEffectParams} from './my-effect/index.js'; ``` ## 4. Build and verify Run the existing tests and build: ```bash cd packages/effects bun test src/test bunx turbo make --filter="@remotion/effects" ``` ## 5. Add docs Create `packages/docs/docs/effects/<effect-name>.mdx`. Follow existing effect pages: - Frontmatter: `slug`, `title`, `sidebar_label`, `crumb: '@remotion/effects'`. - Add `image:` only after running `bun render-cards.ts`. - H1: `# effectName()<AvailableFrom v="..." />`. - Include `_Part of the [@remotion/effects](/docs/effects/api) package._`. - Add a short description. - Add `<EffectsDemo type="effects-<effect-name>" />`. - Add a twoslash example with `title="MyComp.tsx"`. - Document each option as its own `###` heading, using `?` for optional parameters. - Add a `disabled?` section. - Add a See also section. Update: - `packages/docs/sidebars.ts` — add `'effects/<effect-name>'` in alphabetical order. - `packages/docs/docs/effects/table-of-contents.tsx` — add a card in the right category. - `packages/docs/src/data/articles.ts` by running the card generator, not by hand. Use the `writing-docs` skill for documentation wording. ## 6. Add the interactive docs demo Create `packages/docs/components/effects/effects-<effect-name>-preview.tsx`. Use the same preview source as other effects: ```tsx import {myEffect} from '@remotion/effects/my-effect'; import React from 'react'; import {CanvasImage} from 'remotion'; import {EFFECTS_PREVIEW_IMAGE_SRC} from './effects-preview-image'; export const EffectsMyEffectPreview: React.FC<{ readonly amount: number; }> = ({amount}) => { return ( <CanvasImage src={EFFECTS_PREVIEW_IMAGE_SRC} width={1280} height={720} fit="cover" effects={[myEffect({amount})]} /> ); }; ``` Use `fit="cover"` for docs effect previews so the shared preview image fills the 16:9 canvas and does not leave transparent bars. Register the demo in `packages/docs/components/effects-demos/registry.ts`: - Import the preview component and the real effect schema (or read it from `effect().definition.schema`). - Add an entry with `id: 'effects-<effect-name>'`. - Add `initialValues` only for required fields whose schema default is `undefined`. Use the `docs-demo` skill for demo details. ## 7. Add and render the table-of-contents preview composition The TOC card must come from a real Remotion composition in `packages/docs`, not a hand-written asset. Always render preview assets as PNG files. Add a `Still` to `packages/docs/src/remotion/Root.tsx` under the `effect-previews` folder: ```tsx <Still id="effects-my-effect-preview" component={EffectsMyEffectPreview} width={1280} height={720} defaultProps={{ amount: 1, }} /> ``` Use the same `width` and `height` as the preview component's `CanvasImage`. If the preview component uses the shared docs preview image, keep `fit="cover"` on `CanvasImage`. Rendering a 16:9 preview component into a different aspect ratio can leave black bars in the generated TOC image. Then render from `packages/docs`: ```bash bunx remotion still src/remotion/entry.ts effects-my-effect-preview static/img/effects-my-effect-preview.png --overwrite --image-format=png ``` Commit both: - The composition entry in `packages/docs/src/remotion/Root.tsx` - The rendered image in `packages/docs/static/img/` ## 8. Generate docs card Run: ```bash cd packages/docs bun render-cards.ts ``` Commit the generated `packages/docs/static/generated/articles-docs-effects-<effect-name>.png` and the new `image:` frontmatter line. If `render-cards.ts` opportunistically generates unrelated missing cards, remove those unrelated files unless they belong to the current change. ## 9. Update the Remotion skill Keep the agent-facing Remotion skill in sync with the new effect. Update `packages/skills/skills/remotion-markup/effects.md` only if the new effect changes general usage mechanics, import conventions, installation guidance, or custom-effect recommendations. Do not duplicate the full effect list there; use the docs table of contents as the canonical list. ## 10. Format, build, and verify Run: ```bash cd packages/effects bunx oxfmt src --write cd ../.. bun run build bun run formatting ``` If the change touches docs source, `bun run formatting` covers `packages/docs/src`. For MDX-only edits, do not run formatters on docs pages. Before committing, check: ```bash git diff --check git status --short ``` ## Common pitfalls - Do not forget `package.json` `exports` and `typesVersions`; subpath imports like `@remotion/effects/my-effect` depend on them. - Do not forget `bundle.ts`; otherwise the ESM subpath will not be built. - Do not leave temporary render entry points in `packages/docs/src/remotion`. - Do not use a hand-written SVG for the effect TOC preview. - Preserve alpha unless the effect intentionally changes it. - For pixel math, be aware canvases store premultiplied alpha. - WebGL color math often needs to unpremultiply the sampled RGB before luminance or threshold calculations, then premultiply the output RGB again.