Vulkan: Clip clamped depth in geometry shader

[unknownbrackets]

Well, I know I said I hate clipping maths (and I do), but I decided to give it a shot anyway. It seems to work on NVIDIA, and with no noticeable slowdown there compared to not using the geometry shader and using clip distance/etc. Not sure how this'll perform on mobile, since the shader does get a bit more complicated.

Test frame dump:
#11216_UCUS98703_pursuit_force_clamp.zip

Which should look like this:

Note that this is an especially nice test frame dump, because it requires curves and non-curves to be clipped against minz/maxz for proper rendering.

This corrects deformed geometry on Mali devices which don't support user-space clipping but do support depth clamp. I'm not really aware of any other devices this will help, even Apple supports shader clip distance.

With this change, people with Mali GPUs (which are fairly common) ought to avoid most already-solved depth related issues. Apple users still need to turn off hardware transform.

-[Unknown]

[hrydgard]

Renders perfectly on S20 with Mali. nice!

Really nice work!

[ghost]

This might fix #14146 (comment)?

[unknownbrackets]

Well, #16162 would already fix that for devices capable of geometry shaders. That just needs negative Z clip to render properly, it's not related to depth clamp I think.

It still doesn't quite "fix" it, we'd need to clip in software transform and either force software transform or accept that hardware transform will render wrong for people without shader clip distance or geometry shaders.

We probably also could adjust the vertex range culling to clip negative Z even on Apple devices. I'll just do that, I meant to before, I'll just expand the cases a bit.

-[Unknown]