AAA Gaming on Asahi Linux

> Tessellation enables games like The Witcher 3 to generate geometry. The M1 has hardware tessellation, but it is too limited for DirectX, Vulkan, or OpenGL. We must instead tessellate with arcane compute shaders

> Geometry shaders are an older, cruder method to generate geometry. Like tessellation, the M1 lacks geometry shader hardware so we emulate with compute.

Is this potentially a part of why Apple doesn't want to support Vulkan themselves? Because they don't want to implement common Vulkan features in hardware, which leads to less than ideal performance?

(I realize performance is still relatively fast in practice, which is awesome!)

> Is this potentially a part of why Apple doesn't want to support Vulkan? Because they don't want to implement common Vulkan features in hardware, which leads to less than ideal performance?

Yes, it's a big reason.

I tried to port the yuzu switch emulator to macos a few years ago, and you end up having to write compute shaders that emulate the geometry shaders to make that work.

Even fairly modern games like Mario Odyssey use geometry shaders.

Needless to say, I was not enough of a wizard to make this happen!

Why Apple does not just implement it? They have more resources than anyone in the world. Patents?

Are you talking about Vulkan or about geometry shaders? The later is simple: because geometry shaders are a badly designed feature that sucks on modern GPUs. Apple has designed Metal to only support things that are actually fast. Their solution for geometry generation is mesh shaders, which is a modern and scalable feature that actually works.

If you are talking about Vulkan, that is much more complicated. My guess is that they want to maintain their independence as hardware and software innovator. Hard to do that if you are locked into a design by committee API. Apple has had some bad experience with these things in the past (e.g. they donated OpenCL to Kronos only to see it sabotaged by Nvidia). Also, Apple wanted a lean and easy to learn GPU API for their platform, and Vulkan is neither.

While their stance can be annoying to both developers and users, I think it can be understood at some level. My feelings about Vulkan are mixed at best. I don't think it is a very good API, and I think it makes too many unnessesary compromises. Compare for example the VK_EXT_descriptor_buffer and Apple's argument buffers. Vulkan's approach is extremely convoluted — you are required to query descriptor sizes at runtime and perform manual offset computation. Apple's implementation is just 64-bit handles/pointers and memcpy, extremely lean and immediately understandable to anyone with basic C experience. I understand that Vulkan needs to support different types of hardware where these details can differ. However, I do not understand why they have to penalize developer experience in order to support some crazy hardware with 256-byte data descriptors.