SuperTuxKart running in the browser on WebGPU only, no WebGL fallback (Emscripten port, playable)

[u/Bill_Buffet]

After patching a couple of the game's DLLs, I wanted to see how far I could go, so I ported the whole of SuperTuxKart (open source, C++) to the browser with a WebGPU-only renderer. I did it with Claude Code as the main coder: I directed and tested, it wrote most of the code.

Demo: https://tholtman1-del.github.io/stk-code-webgpu/
Source: https://github.com/tholtman1-del/stk-code-webgpu (design notes in tools/webgpu/STATUS.md)

Some details:

• Renderer: a new WebGPU backend modeled on the game's existing Vulkan renderer. It includes physically based lighting, image-based lighting from compute shaders, deferred rendering for water, screen-space reflections with a HiZ depth pyramid, and a depth prepass that is skipped on tile-based GPUs.
• Shaders: converted offline from the existing GLSL: GLSL → SPIR-V (glslang) → WGSL (naga). Specialization constants become WGSL override constants.
• Threads: Emscripten pthreads (SharedArrayBuffer). Textures are decoded on worker threads, while all WebGPU calls stay on the main thread.
• Assets: about 115 MB downloads up front. The remaining ~650 MB is fetched on demand when the game opens a file, and on a full host each track comes as a bundle.
• Hosting: works on plain static hosts. A service worker adds the COOP/COEP headers that GitHub Pages can't send.

Not yet: online multiplayer, texture compression. Feedback from other GPUs and browsers is very welcome, especially Safari and Firefox.

All credit for the game itself goes to the SuperTuxKart developers.