WebGPURenderer: Honor polygonOffset with WebGPU backend.

[Mugen87]

Fixed #30494.

Description

The PR adds Material.polygonOffset support to the WebGPU backend. The WebGL backend already supports it.

Note: The semantics of polygonOffset in WebGPU are different than in WebGL. When understanding the specs correctly, polygonOffsetUnits should be mapped to depthBias and polygonOffsetFactor to depthBiasSlopeScale. It seems that makes the most sense.

WebGPU: https://www.w3.org/TR/webgpu/#dom-gpudepthstencilstate-depthbias
WebGL: https://developer.mozilla.org/en-US/docs/Web/API/WebGLRenderingContext/polygonOffset

@AndrewChan2022 Would this work for you?

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	336.42 78.33	336.42 78.33	+0 B +0 B
WebGPU	517.83 143.85	517.95 143.9	+120 B +45 B
WebGPU Nodes	517.29 143.74	517.41 143.79	+120 B +47 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	465.41 112.17	465.41 112.17	+0 B +0 B
WebGPU	589.7 160	589.82 160	+120 B -3 B
WebGPU Nodes	545.07 149.5	545.19 149.54	+120 B +48 B

[AndrewChan2022]

Fixed #30494.

Description

The PR adds Material.polygonOffset support to the WebGPU backend. The WebGL backend already supports it.

Note: The semantics of polygonOffset in WebGPU are different than in WebGL. When understanding the specs correctly, polygonOffsetUnits should be mapped to depthBias and polygonOffsetFactor to depthBiasSlopeScale. It seems that makes the most sense.

WebGPU: https://www.w3.org/TR/webgpu/#dom-gpudepthstencilstate-depthbias WebGL: https://developer.mozilla.org/en-US/docs/Web/API/WebGLRenderingContext/polygonOffset

@AndrewChan2022 Would this work for you?

I've tested it, and this is exactly what I wanted. Thanks!