OpenGL man pages
glDepthRange - specify the mapping of z values from normalized device
coordinates to window coordinates
void glDepthRange( GLclampd near,
GLclampd far )
near Specifies the mapping of the near clipping plane to window
coordinates. The default value is 0.
far Specifies the mapping of the far clipping plane to window
coordinates. The default value is 1.
After clipping and division by w, z coordinates range from -1.0 to 1.0,
corresponding to the near and far clipping planes. glDepthRange specifies
a linear mapping of the normalized z coordinates in this range to window z
coordinates. Regardless of the actual depth buffer implementation, window
coordinate depth values are treated as though they range from 0.0 through
1.0 (like color components). Thus, the values accepted by glDepthRange are
both clamped to this range before they are accepted.
The default mapping of 0,1 maps the near plane to 0 and the far plane to 1.
With this mapping, the depth buffer range is fully utilized.
It is not necessary that near be less than far. Reverse mappings such as
1,0 are acceptable.
GL_INVALID_OPERATION is generated if glDepthRange is executed between the
execution of glBegin and the corresponding execution of glEnd.
glGet with argument GL_DEPTH_RANGE
Fri Dec 6 11:18:03 EST 1996
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