Fix the output pass cache for multi-canvas rendering

[arodic]

Related issue: #32689

Description

#32690 introduced regression that caused webgpu_multiple_canvas to render same output to all canvases where each canvas should have unique output buffer.

the problem is that this line returns false negative because it only represents output config from getOutputCacheKey(): tone mapping, color space, XR state It does not encode which texture is currently bound

return cacheKey !== this.getOutputCacheKey();

This fix, however feels more like a band-aid rather than something that addresses the real issue. The caching mechanism relies on a cacheKey that does not correctly check for the identity of the target being cached.

I'm submitting this as draft and looking for better solution.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	359.97 85.53	359.97 85.53	+0 B +0 B
WebGPU	632.13 175.39	632.27 175.42	+134 B +31 B
WebGPU Nodes	630.25 175.1	630.38 175.13	+134 B +30 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	492.17 120.11	492.17 120.11	+0 B +0 B
WebGPU	704.56 190.19	704.7 190.22	+134 B +28 B
WebGPU Nodes	653.78 177.6	653.92 177.67	+134 B +72 B

[sunag]

Closing in favor of #33228