Difference between revisions of "Occlusion Query"

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== How do I perform occlusion or visibility testing? ==
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An '''Occlusion Query''' is an OpenGL mechanism that allows the user to determine approximately how many fragments were rasterized when executing a particular sequence of rendering commands.
  
This is wrong!
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OpenGL provides no direct support for determining whether a given primitive will be visible in a scene for a given viewpoint. At worst, an application will need to perform these tests manually.  The previous question contains information on how to do this.
 
 
 
The code example from question 10.010 was combined with Nate Robins' excellent viewing tutorial to produce this [http://lynx.inertiagames.com/~michael/OPENGLTUTORS.zip view culling example code].
 
 
 
Higher-level APIs, such as Fahernheit Large Model, may provide this feature.
 
 
 
HP OpenGL platforms support an Occlusion Culling extension. To use this extension, enable the occlusion test, render some bounding geometry, and call glGetBooleanv() to obtain the visibility status of the geometry.
 
 
 
[[Category:Special Processes]]
 

Revision as of 21:04, 18 May 2010

An Occlusion Query is an OpenGL mechanism that allows the user to determine approximately how many fragments were rasterized when executing a particular sequence of rendering commands.

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