RGBA32Float blending is used, but not supported by WebGPU

[mwyrzykowski]

WebGPU does not support blending on 32-bits per channel RGBA floating point textures, see the chart https://gpuweb.github.io/gpuweb/#plain-color-formats :

However it appears Nanite is attempting to do so: https://github.com/Scthe/nanite-webgpu/blob/a562d80df3da237034bee62d97d87bce0db04967/src/constants.ts#L50C1-L51C1

This is causing a validation error opening https://scthe.github.io/nanite-webgpu/?scene_file=jinxCombined&impostors_threshold=4000&softwarerasterizer_threshold=1360&nanite_errorthreshold=0.1 in Safari / WebKit.

WebKit has one other bug, fixed by https://bugs.webkit.org/show_bug.cgi?id=279266, but with that fix and working around the rgba32float blending issue described here, it appears the nanite demo works in Safari WebKit as well, at least on macOS:

[Scthe]

So for my part, would export const HDR_RENDER_TEX_FORMAT: GPUTextureFormat = 'rgba16float'; be enough? I see I already changed this in Frostbitten hair WebGPU, wish I remembered why.

[mwyrzykowski]

Yes I think so, I don't see any other usages for rgba32float.

I haven't gotten around to building it from source, I just tried the live demo on WebKit's main development branch. So it should also work great in Safari Technology Preview once https://bugs.webkit.org/show_bug.cgi?id=279266 lands in a build, which is usually a few weeks from the point the fix was merged (today).

[Scthe]

Fixed in 64b5471, should be already deployed. No matter how much I HATE the person who posted this repo on Hacker News, at least something good (your fix) resulted from the whole ordeal.

[mwyrzykowski]

Confirmed it's working with your fix and WebKit's on ToT WebKit (macOS with MiniBrowser) - thank you!