I'm Jon Olick. I make shiny things. I simplify.

I presented Sparse Voxel Octrees at Siggraph 2008.

Wednesday, July 8, 2009

Voxel Performance and Requirements

I read lots of papers on voxel rendering techniques and such describing that they achieved 60fps without specifying some of the most important factors.

1) Image Resolution -- This is obviously important, yet some papers seem to magically forget it. It has to run at 60fps or more at HD (720p and 1080p) resolutions in order to be considered for video games.
2) Voxel Resolution -- IE, how deep is the tree? This is very important as each level of the tree adds one more iteration to your traversal loop for every pixel and as such significantly affects performance.
3) Data Transfer Amount / Speed -- This may not be obvious, but it does play an important role. The GPU can do behind the scenes transfers from system ram to video ram, but the bandwidth is only good if you do it in large chunks (many sequential MB). This plays an important role in performance.
4) Cache Responsiveness -- This one shows its ugly head when you look at a scene that you have never seen before. If the cache is not responsive enough, the coarseness of the unloaded oct-tree will show its ugly head. This is primarily more of a quality issue.

Also, I think its important to mention what the system requirements were to run smoothly at those resolutions.
1) How much Video RAM does it consume? If you require more than 2gb of vram SVO/Voxel data, its not realistic for next gen consoles (720, PS4). Even 2gb may be pushing it. Keeping the requirements under 1.5gb is preferable.
2) How much System RAM does it consume? If you have to store the entire volume set in RAM. This is not realistic as most volume sets of a real game will be in the many gigabytes range.
3) What video card were the results computed on? dual GTX 295's may be a sign that the technology is unreasonably expensive.

I would really like it if all voxel papers in the future would mention these things, because its very hard to evaluate otherwise.

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