WebGPURenderer: Export CubeRenderTarget and use it in examples.

[Mugen87]

Related issue: -

Description

This PR refactors an open issue in the WebGPURenderer build. It exports CubeRenderTarget and removes any dependencies to WebGLCubeRenderTarget. WebGLCubeRenderTarget is not exported in Three.Core.js anymore but only Three.js which means it's only available in the WebGLRenderer builds.

WebGLCubeRenderTarget has dependencies to ShaderMaterial and UniformsUtils which are unrelated to WebGPURenderer. The dependencies are caused by fromEquirectangularTexture() which holds material system specific code.

CubeRenderTarget.fromEquirectangularTexture() also holds material system specific code so it can't be placed in Three.Core.js. That's why WebGLCubeRenderTarget can't be derived from CubeRenderTarget as well.

CubeRenderTarget is now derived from RenderTarget and all WebGPU examples now use CubeRenderTarget. This change must be noted in the migration guide since applications must use CubeRenderTarget when they switch to WebGPURenderer.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	357.49 84.84	359.21 85.29	+1.72 kB +448 B
WebGPU	622.71 172.91	622.94 173.01	+236 B +100 B
WebGPU Nodes	621.31 172.67	621.52 172.77	+213 B +96 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	490.47 119.9	490.47 119.49	+0 B -411 B
WebGPU	693.82 188.21	689.6 186.26	-4.21 kB -1.95 kB
WebGPU Nodes	643.2 175.31	638.99 173.68	-4.21 kB -1.63 kB

[Mugen87]

@sunag In the next step, I'm going to update MaterialLoader so it does not import ShaderMaterial and RawShaderMaterial. These material types will be added to the loader's material lib with a new static method in the WebGLRenderer builds. In this way, the WebGPURenderer builds will be free from ShaderMaterial, RawShaderMaterial, any shader chunks and UniformUtils.