improve-threejs

name

improve-threejs

description

Audit and fix Three.js and React Three Fiber apps for frame-loop performance, GPU memory leaks, scene-graph correctness, and visual defects like z-fighting, shadow acne, wrong color space, and broken resize handling. Uses React Doctor as the scanning engine plus a visual rubric checked against rendered output. Use when the user asks to improve, audit, scan, or clean up a Three.js, R3F, react-three-fiber, drei, or WebGL app, or types `/improve-threejs`.

Improve Three.js

Audits a Three.js or React Three Fiber (R3F) codebase and fixes what hurts most: work that runs every frame, GPU resources that never get disposed, scene-graph objects rebuilt on every render, and visual defects the user can see. React Doctor supplies the machine-verified code scan; this skill supplies the frame-loop judgment and the visual inspection a general React scanner lacks.

The core principle: severity follows the render loop. Code inside useFrame or a requestAnimationFrame callback runs 60 times per second, so a minor inefficiency there outweighs a major one in a settings panel. Rank every finding by where it runs, not by the rule's default severity.

Workflow

Step 1: Recon

Identify the stack before scanning: plain Three.js or R3F, which helper libraries are in use (drei, postprocessing, rapier), and where the render loop lives (useFrame hooks, requestAnimationFrame, the <Canvas frameloop> setting).

Build a hot-path map: every useFrame body, every RAF callback, every pointer-move handler. These files get the strictest review in Step 3.

Step 2: Scan

Run React Doctor read-only to collect structured evidence:

npx react-doctor@latest --verbose

For a regression check after making changes, run with --scope changed and confirm the score did not drop.

Step 3: Triage by frame-loop leverage

Re-rank the scanner's findings using the hot-path map, then hunt for the Three.js-specific problems the scanner cannot see. Confirm every finding at its file:line before reporting it.

HIGH severity, runs every frame or leaks GPU memory:

• Allocation inside useFrame: new Vector3(), new Color(), or fresh arrays passed to Three.js APIs each frame. Fix: hoist a scratch object to module scope or useMemo, then mutate it in place
• setState inside useFrame: re-renders the React tree on every frame. Fix: mutate refs directly; reserve state for discrete changes like selection or visibility
• Missing disposal: geometries, materials, textures, or render targets created imperatively and never disposed. Fix: call dispose() in the cleanup function, or move the object into R3F's declarative tree so it owns the lifecycle
• Object reconstruction in render: geometry or material instances created without useMemo, or inline args arrays whose identity changes each render, forcing R3F to rebuild the underlying object

MEDIUM severity, per-render or per-interaction waste:

• Unstable scene-graph props: inline new THREE.Vector3() or fresh material objects as props (plain arrays like position={[x, y, z]} are fine; R3F handles them)
• Missing instancing: hundreds of identical meshes rendered individually instead of through <Instances> or InstancedMesh
• Wasted frames: frameloop="always" on a scene that only changes on interaction. Fix: frameloop="demand" plus invalidate()
• Uncached asset loading: textures and models loaded outside useLoader, useTexture, or useGLTF, losing caching and Suspense integration

LOW severity, hygiene: React Doctor findings on non-canvas UI code, missing <Preload>, oversized textures.

Step 4: Visual audit

Inspect what the scene actually renders. Every visual finding needs evidence: a screenshot, a frame capture, or a reproduced observation, never a guess from reading source. When a dev server and browser are available, load the app, capture the first stable frame, then capture again after moving the camera and interacting. When no browser is available, check the code-level causes listed below and label each finding as inferred from source.

Apply the mini rubric. A row fails only when the evidence shows the failure condition:

Area	Check	Fail when
Render sanity	The scene reaches a stable frame after load	Black canvas, WebGL context errors, or content that never appears
Geometry	Move the camera along seams, edges, and boundaries	Gaps, missing faces, visible backfaces, or two surfaces flickering at the same depth (z-fighting)
Transparency and depth	Cross depth-order boundaries with overlapping or transmissive surfaces	Wrong sort order, halos, opaque surfaces that should transmit, or flicker at grazing angles
Textures	View mapped surfaces close, far, and at grazing angles	Missing textures, stretching, seams, moiré, shimmer, or washed-out colors from a wrong color space
Materials and lighting	Change light and view direction on lit surfaces	Surfaces that ignore light direction, or reflective metals with no environment to reflect
Shadows	Move casters, receivers, and the light through their range	Acne, detached or floating shadows, flicker at rest, or shadows that outlive their caster
Camera	Follow the primary subject through movement and transitions	Subject leaves frame, camera clips into geometry, or foreground blocks the play area
Scale and contact	Compare object scale and resting contact against surroundings	Objects float above, sink into, or intersect their support surface, or sit at implausible scale
Image stability	Pan the camera slowly at supported resolutions	Silhouettes, thin geometry, or highlights that crawl, sparkle, or ghost
Resize and DPR	Change viewport size, zoom, and device pixel ratio	Distortion, blur, stretched output, or content leaving the viewport

Each rubric row has a small set of usual code-level causes. Check these first when a row fails:

• Washed-out or too-dark colors: renderer.outputColorSpace not set to SRGBColorSpace, color textures missing texture.colorSpace = SRGBColorSpace, or a data texture (normal, roughness) wrongly marked sRGB
• Z-fighting: coplanar geometry needing polygonOffset or a position nudge, or a near plane set far too small for the scene scale
• Shadow acne or floating shadows: shadow.bias and shadow.normalBias untuned, or a shadow camera frustum far larger than the scene
• Blurry or stretched canvas: renderer size not synced to canvas CSS size, setPixelRatio never called, or a resize handler that forgets camera.updateProjectionMatrix()
• Black metals: metalness: 1 with no scene.environment set
• Transparency sorting glitches: large transparent meshes needing depthWrite: false, manual renderOrder, or a split into smaller meshes
• Shimmer and crawl: missing texture anisotropy, antialiasing disabled, or thin geometry needing thicker forms

Step 5: Fix

Fix in severity order: HIGH performance findings and failed visual rows first. When a finding maps to a React Doctor rule, fetch the canonical recipe instead of improvising:

https://www.react.doctor/prompts/rules/<plugin>/<rule>.md

For Three.js-specific findings, apply the fix named in the triage list or the cause list above.

Step 6: Validate

Run npx react-doctor@latest --verbose --scope changed and confirm the score did not regress. Re-check every visual rubric row that failed, using the same viewpoint and interaction as the original evidence, and confirm it now passes. Then verify behavior: the scene renders, animations play, and interactions respond. If browser dev tools are available, watch the memory profile while orbiting an idle scene; a rising heap during idle means a disposal leak survived.

Checks the scanner always misses

Review these by hand on every audit:

• dispose() coverage for every imperatively created GPU resource
• Allocations and setState inside useFrame and RAF callbacks
• Event listeners and ResizeObservers on the canvas or window without cleanup
• Raycasting against the full scene on every pointer move instead of a filtered target list
• Shadows or postprocessing enabled globally when one part of the scene needs them
• Color space configuration on the renderer and every color texture