Occlusion algorithm

Hey there,

Try looking at www.gamasutra.com in the programming section for fast outdoor occlusion culling article, or something of that name, which discusses the techniques you are probably referring to.

hirachical viewing frustrum culling reduces geometry
occlusion culling reduces fillrate

So I ask, what limits your brute force implementation?
I mean could you please list fps for different resolutions?

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occlusion culling reduces fillrate

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Occlusion culling reduces both geometry and fillrate. But besides that, DumbBill, he is right that you need to know your bottlenecks. Although generally I would tend to say that there is something wrong with your code, if you don''t feel a difference between frustum culled and brute force (normally, the difference is huge), but there are situations, where no speedup will occur. Especially low-poly count scenes, here the overhead of culling might outweight the overhead of just rendering the additional faces and let the hardware clip it. How much faces is your scene ? Pick a certain test frame. How much faces are in the view ? And what is the speedup you gain on that particular frame ?

You said, you were using an octree. How do you organize and render geometry ? Do you traverse each an every polygon, or do you send a vertex buffer/array per octree node ?

About occlusion mapping, you could check out this paper. But I would seriously consider fixing the frustum culling first, if I were you.

/ Yann

an article on gamasutra site: occlusion culling algorithms

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How do you organize and render geometry ? Do you traverse each an every polygon, or do you send a vertex buffer/array per octree node ?

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If faces in an octree node are associated with different render states/textures, is it better to first traverse all octree nodes and group faces with same render state together?

Yes it is.
State change is what slow down graphic cards the most.
(and a few tech, like stencil shadow volumes which are fast on only the latest hardware [GFFX, R300])


-* So many things to do, so little time to spend. *-