Add Effect Agent Skill

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:

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:

export {myEffect, type MyEffectParams} from './my-effect/index.js';

4. Add tests

Update packages/effects/src/test/effect-params.test.ts:

• Import the new effect.
• Add it to the documentation link test.
• Test default params when all fields are optional.
• Test required params if any are required.
• Test invalid values and exact error substrings.
• Test that meaningful params produce distinct effectKey values.

Run:

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 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:

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:

<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:

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:

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:

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:

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.