# Use one gl_CullDistance values to "cull" away a vertex with a negative value
# supplied to 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 insider 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.

[require]
GLSL >= 1.30
GL_ARB_cull_distance

[vertex shader]
#version 130
#extension GL_ARB_cull_distance: enable

out float gl_CullDistance[1];

void main(void)
{
         gl_Position = gl_Vertex;

         gl_CullDistance[0] = -1.0;
}

[fragment shader]
#version 130

void main(void)
{
         gl_FragColor = vec4(1, 0, 0, 1);
}

[test]
clear color 0.0 1.0 0.0 1.0
clear
draw rect -1 -1 2 2

probe all rgba 0.0 1.0 0.0 1.0