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| == How do I perform occlusion or visibility testing? ==
| | 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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| 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.
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| 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].
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| Higher-level APIs, such as Fahernheit Large Model, may provide this feature.
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| 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.
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| [[Category:Special Processes]]
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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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