alt Hacker News> 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!)
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Metal 3 (in 2022) added mesh shaders, which can be used to emulate geometry shaders.
We (CodeWeavers) are doing this in (a fork of) MoltenVK, and Apple’s D3DMetal is as well.
Apple not supporting Vulkan is a business decision. They wanted a lean and easy to learn API that they can quickly iterate upon, and they want you to optimize for their hardware. Vulkan does not cater to either of these goals.
Interestingly, Apple was on the list of the initial Vulkan backers — but they pulled out at some point before the first version was released. I suppose they saw the API moving in the direction they were not interested in. So far, their strategy has been a mixed bag. They failed to attract substantial developer interest, at the same time they delivered what I consider to be the best general-purpose GPU API around.
Regarding programmable tessellation, Apple's approach is mesh shaders. As far as I am aware, they are the only platform that offers standard mesh shader functionality across all devices.
Geometry shaders are not part of base Vulkan. They're an extension.
That might be an excuse, but that's hardly a reason. They are simply extreme lock-in proponents and don't want to support cross platform graphics API. That's the real reason.
> 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!