Editing Hidden-surface determination (section)

=== Occlusion culling ===
{{See also|Z-buffering#Z-culling}}
Objects that are entirely behind other opaque objects may be culled. This is a very popular mechanism to speed up the rendering of large scenes that have a moderate to high [[depth complexity]]. There are several types of occlusion culling approaches:
* [[Potentially visible set]] (''PVS'') rendering divides a scene into regions and pre-computes visibility for them. These visibility sets are then indexed at run-time to obtain high-quality visibility sets (accounting for complex occluder interactions) quickly.
* [[Portal rendering]] divides a scene into cells/sectors (rooms) and portals (doors), and computes which sectors are visible by clipping them against portals.

Hansong Zhang's dissertation "Effective Occlusion Culling for the Interactive Display of Arbitrary Models"<ref>{{cite web |url=http://www.cs.unc.edu/~zhangh/hom.html |title=Occlusion Culling with Hierarchical Occlusion Maps |website=www.cs.unc.edu}}</ref> describes an occlusion culling approach.