gl_CullDistance

provides a mechanism for controlling user culling

Signature

gl_CullDistance( )->

Description

The
gl_CullDistance
variable provides a mechanism for controlling user culling. The element gl_CullDistance [ i ] specifies a cull distance for each plane i . A distance of 0.0 means that the vertex is on the plane, a positive distance means that the vertex is inside the cull volume, and a negative distance means that the point is outside the cull volume. Primitives whose vertices all have a negative clip distance for plane i will be discarded.
The
gl_CullDistance
array is predeclared as unsized and must be sized by the shader either by redeclaring it with an size or by indexing it only with integral constant expressions. The size determines the number and set of enabled cull distances and can be at most
gl_MaxCullDistances
. The number of varying components consumed by
gl_CullDistance
will match the size of the array. Shaders writing
gl_CullDistance
must write all enabled distances, or culling results are undefined.
As an output variable,
gl_CullDistance
provides the place for the shader to write these distances. As an input in all but the fragment language, it reads the values written in the previous shader stage. In the fragment language, the
gl_CullDistance
array contains linearly interpolated values for the vertex values written by a shader to the
gl_CullDistance
vertex output variable.
It is a compile-time or link-time error for the set of shaders forming a program to have the sum of the sizes of the
gl_ClipDistance
and
gl_CullDistance
arrays to be larger than
gl_MaxCombinedClipAndCullDistances
.

Version Support

gl_CullDistance

See Also

Copyright

Copyright
2014 Khronos Group. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. .