The CPU feeds commands (CommandBuffers) telling the GPU what to do over a Queue.
WebGPU/wgpu/dawn only have a single general purpose queue. Meaning any data upload commands (copyBufferToBuffer) you send on the queue block rendering commands from starting.
The solution is multiple queues. Modern GPUs have a dedicated transfer/copy queue separate from the main general purpose queue.
WebGPU/wgpu/dawn would need to add support for additional queues: https://github.com/gpuweb/gpuweb/issues?q=is%3Aopen+is%3Aiss...
There's also ReBAR/SMA, and unified memory (UMA) platforms to consider, but that gets even more complex.
Yes. This is the big performance advantage of Vulkan over OpenGL. You can get the bulk copying of textures and meshes out of the render thread. So asset loading can be done concurrently with rendering.
None of this matters until you're rendering something really big. Then it dominates the problem.
I haven't tried it yet, but will try soon for my open-source metaverse Substrata: https://substrata.info/.
Long version: https://github.com/gfx-rs/wgpu/discussions/5525
There's a lock stall around resource allocation. The asset-loading threads can stall out the rendering thread. I can see this in Tracy profiilng, but don't fully understand the underlying problem. Looks like one of three locks in WGPU, and I'm going to have to build WGPU with more profiling scopes to narrow the problem.
Very few people have gotten far enough with 3D graphics in Rust to need this. Most Rust 3D graphics projects are like the OP's here - load up a mostly static scene and do a little with it. If you load all the content before displaying, and don't do much dynamic modification beyond moving items around, most of the hard problems can be bypassed. You can move stuff just by changing its transform - that's cheap. So you can do a pretty good small-world game without hitting these problems. Scale up to a big world that won't all fit in the GPU at once, and things get complicated.
I'm glad to hear from someone else who's trying to push on this. Write me at "nagle@animats.com", please.
For a sense of what I'm doing: https://video.hardlimit.com/w/7usCE3v2RrWK6nuoSr4NHJ
