Canvas Threejs

Use when building or reviewing Canvas 2D, Three.js/WebGL, React Three Fiber, GLSL shaders, ShaderToy-to-WebGL adaptation, 2D/3D visualization, game rendering, animation loops, GPU resource cleanup, or rendering performance. Do not use for standard DOM UI, charts already covered by a chart library, o

Canvas and Three.js

Purpose

Enable high-performance 2D/3D graphics rendering in the browser.

Procedure

1. First select the rendering layer: DOM for standard UI; Canvas 2D for simple 2D graphics/signatures/particles; Three.js/WebGL for 3D models, spatial interactions and complex particles; React Three Fiber for declarative 3D in React projects.
2. Define stable size, DPI adaptation, and resize behavior for the render container; Canvas does not automatically scale cleanly with CSS.
3. The animation loop uses requestAnimationFrame, which is paused when it is invisible or has no changes, and canceled when it is uninstalled.
4. Three.js must release geometry/material/texture/renderer and remove event listeners and observers.
5. Shader/WebGL tasks first identify whether it is an SDF, ray marching, noise, particle, post-processing, multipass or debugging issue, and then decide whether native WebGL2, Three.js ShaderMaterial or R3F is required.
6. Check the GLSL version, entry function, varying/in-out, texture API, uniform usage and function declaration order when adapting to WebGL2 to avoid white screen leaving only console errors.
7. Provide aria-label, alternative text or DOM summary for inaccessible graphic content; interactive graphics must have keyboard support.

Core Patterns

ts

const dpr = Math.min(window.devicePixelRatio || 1, 2);
canvas.width = width * dpr;
canvas.height = height * dpr;
canvas.style.width = `${width}px`;
canvas.style.height = `${height}px`;
ctx.scale(dpr, dpr);

ts

let animationId = 0;
function animate() {
  animationId = requestAnimationFrame(animate);
  renderer.render(scene, camera);
}

return () => {
  cancelAnimationFrame(animationId);
  geometry.dispose();
  material.dispose();
  renderer.dispose();
};

Detailed reference

Load references/rendering-patterns.md when it comes to Canvas 2D drawing, animation loops, Three.js scene building, React Three Fiber, InstancedMesh, and performance cleanup.

Load references/shader-webgl-patterns.md when it comes to shader routing, WebGL2 adaptation, GLSL debugging, multi-pass budgeting, and visual verification.

Constraints

• Canvas/WebGL content is not visible to screen readers and alternative semantics must be provided.
• WebGL consumes GPU, and low-end devices need to limit the pixel ratio, number of faces and texture size.
• Three.js resources will not be released automatically, and missing dispose() will cause GPU memory leaks.
• Canvas responsive must synchronize CSS dimensions, drawing dimensions, and camera/viewport.
• Complex layout/path planning can be combined with the background thread workflow, but the rendering itself is still coordinated on the main thread/rendering thread.
• The Shader main loop, number of sampling layers, and number of multi-passes must be budgeted; on low-end devices, reduce the DPR, number of steps, number of particles, or disable heavy post-processing.
• Before delivery, you must confirm that the canvas is not empty, has the correct size, is not stretched after resize, and has no shader compile/link errors in the console.

Expected Output

2D/3D scenes are crisp, responsive, cleanable, and close to 60fps on key devices; users can understand/operate with core content via alt text or keyboard paths.