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Occlusion: visibility umbra

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Have anyone tried occlusion culling throw "virtual occluders" / "visibility umbra", how good is it and will it work good for indoor and outdoor environments? How fast is it compared to HW occlusion and HOM? I think it’s called “virtual occluders” or “visibility umbra” or similar. Here are tow links: http://andyc.org/articles/viewarticle.php?id=7 http://www.gamasutra.com/features/20020717/bacik_pfv.htm Do anyone have any good papers/links on the subject? /Luger

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Virtual occluders and visibility umbra works with both indoor/outdoor environements, but for indoor environments cells and portals or BSP trees are much better. Unfortunately, they are object space algorithms and they behave well with scenes with "few" polygons or with big occluder (for visibility umbra, often resoved by occlusion trees). On the other side HW occlusion and HOM are image-space algorithms (they can take any scene in input, not only polygonal ones) that works quite well and that avoids robustness issues that can occur with object space algorithms. They also have drawback : HW occlusion have latency since it's executed on the GPU (that can bee minimized using Bitner's method for exemple, but not avoided), and HOM have fillrate problems since you can take a lot of time to rasterize the silouhettes (and to compute them). As it's said in the article you mention, the best solution is to combine them all.

You can find one of the most complete list of papers on visibility here :
http://artis.imag.fr/~Xavier.Decoret/bib/visibility/

Here are my favorite ones :
http://www.cgg.cvut.cz/~bittner/publications/cgi98-copy.pdf
http://csdl.computer.org/comp/mags/cg/2004/02/g2086abs.htm
http://www.cg.tuwien.ac.at/research/vr/chcull/
http://pubs.cs.uct.ac.za/archive/00000140/

ptl

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