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Layers All the Way Down: The Untold Story of Shader Compilation

We tried something like this with piet-gpu-hal. One problem is that spirv-cross is lossy, though gaps in target language support are getting better. For example, a device scoped barrier is just dropped on the floor before Metal 3.2. Atomics are also a source of friction.

But the main problem is not the shader language itself, but the binding model. It's a pretty big mess, and things change as you go in the direction of bindless (descriptor indexing). There are a few approaches to this, certainly reinventing WebGPU is one. Another intriguing approach is blade[1] by Dzmitry Malyshau.

I wish the authors well, but this is a hard road, especially if the goal is to enable more advanced features including compute.

[1]: https://github.com/kvark/blade

6 months agoby raphlinus

BGFX (https://github.com/bkaradzic/bgfx) uses a different approach. You basically write your shader in a GLSL-like language but it's all just (either very clever or very horrible) macro expansions that handles all the platform differences. With that you get a very performant backend for OpenGL, WebGL, Vulkan, Metal, Direct3D 11 and 12 and Playstation. It's shader compiler program basically does minimal source level transformations before handing it over to the platforms' own shader compiler if available.

6 months agoby riggsdk

> Rendering, by comparison, is a huge can of worms. Every platform has their own unique support matrix.

GPU APIs landscape is stuck in the dumb NIH mentality of the '90s because stuck up lock-in proponents refuse to support Vulkan on their walled gardens.

The only recent somewhat positive development about that was MS deciding to use SPIR-V and eventually ditch DXIL. A small step in the right direction, but not really enough yet.

6 months agoby shmerl

This is a very interesting article, it was fun to learn what shaders are and why I have to wait for them to compile every time I play Call of Duty.

What I'd like to know is why game developers can't provide a service / daemon that will perform shader compilation when shaders or drivers change so I don't need to waste 25 minutes of my precious gaming time when I load CoD and see they need compiling. My computer has been sitting there unused all week. Steam was smart enough to download game updates in that time, why isn't your game smart enough to recompile my shaders on an idle machine?

6 months agoby mvdtnz

I really like the WebGPU API. That's the API where the major players, including Apple and Microsoft, are forced to collaborate. It has real-world implementations on all major platforms.

With the wgpu and Google dawn implementations, the API isn't actually tied to the Web, and can be used in native applications.

6 months agoby pornel

If you need to compile shaders at runtime, then why do I have to wait 10 mins for unreal to compile 30,000 shaders whenever it feels like it?

6 months agoby voidUpdate