Meshes using vertex colors sometimes turn black when reflected

[cubeghost]

Describe the bug

When a mesh uses vertex colors and is reflected on other surfaces, the mesh and its reflections intermittently turn completely black.

Expected behavior

The vertex colors are used

Screenshots and Repro Model

Demo: https://observablehq.com/d/79fa68b9ec0780b0

case	screenshot
without path tracing
expected
bug

Platform:

• Device: Desktop
• OS: macOS
• GPU: Apple M3
• Browser: Chrome (also replicated in Firefox and Safari)
• Browser Version: 143.0.7499.110
• Three.js version: r180
• Library version: latest from github (d4e7248)

[gkjohnson]

Thanks for the report. For now the project only supports 4-component, "RGBA" color components. You can see in the changes from #257. The "simple" solution here is to probably process any geometry with an RGB color attribute into RGBA before rendering it. This could be done automatically in the "StaticGeometryGenerator" as well, though, if you'd like to look into a PR.

[gkjohnson]

With the WebGPUPathTracer becoming the priority for the project I'm going through and closing all issues related to the WebGLPathTracer specifically to try to clean things up. Once the WebGPUPathTracer is released we'll plan to remove the WebGLPathTracer from the project (see #779).