Workgraphs is a new feature added recently to DirectX12 with hardware support from NVidia and AMD. It aims to enable a GPU to produce and consume work without involving the CPU in dispatching that work. I spent some time the past couple of weeks experimenting with workgraphs and I’ve put together this high level tutorial on how one can go about using them.

I cobbled together parts I already had in the toy engine to implement a shadow raytracer, comprised of 3 steps: first isolate and filter out pixels that are backfacing to the light (and as such are always is shadow), raymarch the surviving pixels towards the light looking for hits in the depth buffer and then, for pixels that failed to find a hit, raytrace using the acceleration structure. The technique, even if a bit contrived and maybe not too practical, it provides us with many opportunities to produce and consume work on the GPU.

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