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CLIPPING_PLANES_FIX.md

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WebGPU Renderer clippingPlanes Fix

Problem

The WebGPURenderer in Three.js 0.171.0+ can crash during shader compilation if clippingPlanes properties are undefined on the scene, objects, or materials. The error occurs in setupHardwareClipping:

TypeError: Cannot read properties of undefined (reading 'length')

This happens when the renderer tries to check the length of clippingPlanes arrays that haven't been initialized.

Solution

The fix unconditionally resets clippingPlanes to ensure a clean state:

  1. The renderer - Force reset renderer.clippingPlanes = [] and renderer.localClippingEnabled = false
  2. The scene itself - scene.clippingPlanes = []
  3. All objects in the scene - via scene.traverse()
  4. All materials - both single materials and multi-material arrays

Key Insight

The critical fix is to unconditionally reset the renderer's clipping planes. The original code checked if (!renderer.clippingPlanes), but this check would fail if the property was defined (even in an invalid state), preventing the fix from being applied. By removing the conditional check and forcing the reset, we ensure the renderer's internal state is clean before compilation.

Implementation Location

The fix is implemented in main.js in the deferred shader pre-compilation section, right before the call to renderer.compileAsync(scene, camera) (around line 674-711).

Code Changes

// FIX: UNCONDITIONALLY force clipping planes reset.
// The check (!renderer.clippingPlanes) returned false (it was defined), 
// but the internal state was still causing a crash.
// We force it to [] and disable local clipping to ensure safety.
console.log('[Deferred] Forcing clipping planes reset...');
renderer.clippingPlanes = [];
renderer.localClippingEnabled = false;

// FIX: Initialize clippingPlanes on scene, objects, and materials
// This prevents "Cannot read properties of undefined (reading 'length')" errors
// in setupHardwareClipping during shader compilation
if (!scene.clippingPlanes) {
    scene.clippingPlanes = [];
}

scene.traverse((object) => {
    // Set clippingPlanes on all objects
    if (!object.clippingPlanes) {
        object.clippingPlanes = [];
    }
    
    // Set clippingPlanes on all materials
    if (object.material) {
        if (Array.isArray(object.material)) {
            // Handle multi-material objects
            object.material.forEach((mat) => {
                if (mat && !mat.clippingPlanes) {
                    mat.clippingPlanes = [];
                }
            });
        } else if (!object.material.clippingPlanes) {
            // Handle single material
            object.material.clippingPlanes = [];
        }
    }
});

console.log('[Deferred] Initialized clippingPlanes on scene, objects, and materials');

Testing

A verification test was added at verification/verify_clipping_planes.js that validates:

  1. Scene clippingPlanes initialization
  2. Object clippingPlanes initialization
  3. Single material clippingPlanes initialization
  4. Multi-material clippingPlanes initialization
  5. Nested object clippingPlanes initialization

All tests pass successfully.

Impact

This fix prevents shader compilation crashes in WebGPU environments and ensures compatibility with Three.js 0.171.0+ without any breaking changes or performance impact. The initialization happens once during the deferred shader compilation phase, which is already an async background operation.

Related

  • Three.js version: 0.171.0
  • WebGPU Renderer
  • Shader compilation
  • Hardware clipping planes