glDepthRange - specify mapping of depth values from normalized device coordinates to window coordinates
void glDepthRange(GLclampd nearVal, GLclampd farVal);
After clipping and division by w, depth coordinates range from -1 to 1, corresponding to the near and far clipping planes. glDepthRange specifies a linear mapping of the normalized depth coordinates in this range to window depth coordinates. Regardless of the actual depth buffer implementation, window coordinate depth values are treated as though they range from 0 through 1 (like color components). Thus, the values accepted by glDepthRange are both clamped to this range before they are accepted.
The setting 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 nearVal be less than farVal. Reverse mappings such as nearVal = 1, and farVal = 0 are acceptable.
glGet() with argument GL_DEPTH_RANGE
glDepthFunc(), glPolygonOffset(), glViewport()
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