glDepthRange − specify mapping of depth values from normalized device coordinates to window coordinates
void glDepthRange( GLclampd near_val,
GLclampd far_val )
Specifies the mapping of the near clipping plane to window coordinates. The initial value is 0.
Specifies the mapping of the far clipping plane to window coordinates. The initial value is 1.
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 near_val be less than far_val. Reverse mappings such as $"near_val" ~=~ 1$, and $"far_val" ~=~ 0$ 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
glDepthFunc(3G), glPolygonOffset(3G), glViewport(3G)
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