17:03 <yuni> I've been looking into why Inochi2D rendering doesn't work on the Asahi GPU driver in Mesa.

17:04 <yuni> lina gave me an apitrace of her model, which I can replay on macOS with the apitrace patches I wrote a few weeks ago.

17:04 <yuni> With upstream Mesa, the trace triggers a GPU fault. Nothing renders.

17:04 <yuni> I've isolated the issue to two driver bugs:

17:06 <yuni> 1. Stencil buffers and stencil testing are broken. There are a number of bugs affecting stencil. The most obvious is a flag that the driver has to set to enable stencil testing, which Mesa was failing to do. Setting that flag fixes a number of tests related to stencil.

17:07 <yuni> Less obvious, some configuration of the stencil buffer in memory is causing GPU faults in certain circumstances. I'm not sure yet why, or how to fix it. I don't think Lina's setup is affected by this bug, but it should still be fixed.

17:08 <yuni> 2. The texture layout code is incorrect. The faults with Lina's trace seem to result from *underallocating* texture memory. Lina makes heavy use of mipmapping, which has special requirements for allocation. There's an issue with that. I don't think that's anything we can't fix with a bit of reverse-engineering and some unit tests, though.

17:09 <yuni> All that said, it's pretty close to working on top of macOS. I guess Alyssa did an okay job after all.