gl_CullDistance — provides a mechanism for controlling user culling
gl_CullDistance is a member of the
gl_PerVertex named block:
out gl_PerVertex {
vec4 gl_Position;
float gl_PointSize;
float gl_ClipDistance[];
float gl_CullDistance[];
};
In fragment shaders, it is intrinsically declared as:
in float gl_CullDistance[] ;
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.
| OpenGL Shading Language Version | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Variable Name | 1.10 | 1.20 | 1.30 | 1.40 | 1.50 | 3.30 | 4.00 | 4.10 | 4.20 | 4.30 | 4.40 | 4.50 |
| gl_CullDistance | - | - | - | - | - | - | - | - | - | - | - | ✔ |
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. http://opencontent.org/openpub/.