Missing draw_id builtin

[Bromles]

There are multi_draw_* methods on RenderPass (https://docs.rs/wgpu/latest/wgpu/struct.RenderPass.html#method.multi_draw_indirect), but it seems like Naga doesn't support draw_id builtin for that (https://docs.rs/naga/latest/naga/enum.BuiltIn.html)

So the question is - how can I access index of draw call inside vertex shader when using multi_draw_* methods like in OpenGL and Vulkan?

[Bromles]

Was answered in wgpu matrix channel.

Currently, there is no way to use draw_id, because DX12 only just got support for it. There is a way to emulate this with compute, but it's non-trivial