Viewing frustum

Frustum culling is a principle from the 3D computer graphics. Here, it is tested whether an observed object is in the field of vision. " Cull " comes from English and means as much as selection, cutting away, waste. Frustum culling thus means a total of as much as truncated readout.

The frustum is a truncated pyramid whose base the far clipping plane, ie the region behind which nothing is to be drawn is. The section plane is the near clipping plane, everything in front of this plane, so is virtually behind the viewer. The side walls of the pyramid are the planes that are exactly on the screen.

To lie in the visible region, a dot ( German: truncated cone ) within the so-called frustum are. To avoid having to calculate each point of an object individually, simple Hüllobjekte are enabling faster calculation ( engl. "bounding volume" ) defined as boxes or spheres around the objects and performed a cut test between the envelope object and the viewing volume ( frustum ). If the intersection of the volume of the frustum and the volume of Hüllobjekts zero ( an empty set ), it is not the object visible on the screen. If the volume of the Hüllobjekts completely in the frustum, then the object is completely visible. Does another intersection, the object is only partially visible under certain circumstances.