WebGPURenderer: copyFramebufferToTexture - support for post-rendering usage

[sunag]

Related issue: Fixes #29713

Description

Added support for post-rendering usage.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	691.67 171.43	691.67 171.43	+0 B +0 B
WebGPU	820.19 221.32	820.85 221.46	+653 B +140 B
WebGPU Nodes	819.7 221.19	820.36 221.32	+653 B +137 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	463.82 112.17	463.82 112.17	+0 B +0 B
WebGPU	541.03 146.24	541.68 146.38	+654 B +143 B
WebGPU Nodes	497.03 136.06	497.68 136.21	+654 B +145 B

[Mugen87]

I'm testing with a WebGPU port of webgl_framebuffer_texture: https://jsfiddle.net/g0ahteof/1/

With this PR, I get the following runtime error with WebGPU:

Uncaught TypeError: Failed to execute 'copyTextureToTexture' on 'GPUCommandEncoder': Value is not of type 'unsigned long'.
    at WebGPUBackend.copyFramebufferToTexture (WebGPUBackend.js:1524:1)
    at WebGPURenderer.copyFramebufferToTexture (Renderer.js:1316:1)
    at Animation.animate [as animationLoop] (webgl_framebuffer_texture:186:14)
    at update (Animation.js:27:1)

The WebGL backend produces no error but the top left view is empty (so the copy does not work yet).

[sunag]

The last commit fix the WebGPUBackend but seems that y-axis is fliped.

[Mugen87]

When I flip the uv coordinates of the sprite which displays the FramebufferTexture, the result is as expected. I'm using:

sprite.geometry = flipY( sprite.geometry );

function flipY( geometry ) {

	const uv = geometry.attributes.uv;

	for ( let i = 0; i < uv.count; i ++ ) {

		uv.setY( i, 1 - uv.getY( i ) );

	}

	return geometry;

}

[sunag]

I would like to revisit this function of the API soon, there are still some revisions related to color outputs that need to be done.