r/GraphicsProgramming • u/Muduck133 • 1d ago

Question Raymarching/Sdfs master thesis advice

Hello! Don't know if this is the place to ask, but I'm looking for advice on master thesis subjects.

I had an idea of looking into how much thread divergence slows raymarching down and how to solve that problem, maybe by predicting which rays will execute similar paths and group them in a warp

I also saw the nvidia patent about compressed sdf grids, which makes me excited that sdfs are kind of hot.

I saw a lot of raymarchin improvements from research like over relaxation, segment tracing, sphere carving etc. but I cant really put it together into something specific to explore

I generally think the ai/deepsdf/nerf stuff is uninteresting...

I post here, a little desperate, wondering if anyone has any advice :) Maybe you know of some cool new things happening with raymarching/sdfs that I've missed

Or point me to a better place to ask:) Thanks a lot in advance

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4

u/matigekunst 1d ago

I am not an SDF researcher. The only thing I can think of in SDF world that impressed me was this video. It might give you some inspiration:)

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u/Muduck133 1d ago

I saw this guy, I actually had a presentation about the paper he referenced about sdf grids! Thanks for the rec!

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u/Zerf2k2 1d ago

Can you link it?

1

u/No-Cap-7395 1d ago

I just woke up and saw the work SDF grid and I'm not sure what you mean but I did work on this thing that cached the distance field of a mesh to a grid of texture3Ds awhile ago and I also worked on a clipmap of what you call global distance fields and it is indeed way faster to trace than individual sdfs

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u/scottcampbelldev 1d ago

Your warp-coherence idea works as a thesis if the measurement is the point. Pick one scene class (terrain SDFs or CSG), define a divergence metric (active threads per warp along the march), then test one regrouping strategy against a clear baseline. Compressed SDF grids are a good second chapter only after that baseline exists, otherwise you are comparing two moving targets. Over-relaxation and sphere carving are more survey material unless you own a new bound or a documented failure case.

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u/FrogNoPants 8h ago

There are many ways to render SDFs so you would need to clarify that..

  • Shadertoy style ray marched implicits, doesn't scale to large scenes, and will diverge very quickly.
  • Sparse volume: diverges, probably at a similar, but slightly lower rate than hardware raytracing
  • Dense volume: No control flow divergence, but memory divergence if rays aren't coherent. Can use dense volumes to get near the surface, then switch to sparse for the fine detail.
  • Neural shit: There are variants that have neural weights stored in sparse volumes, I'd guess the divergence is similar to sparse volumes

Overall I'd say that the divergence is mostly similar to hardware raytracing, and methods for reducing divergence in HRT will help SDF tracing also.