osx man page for gldepthrange

GLDEPTHRANGE(3G)														  GLDEPTHRANGE(3G)

NAME
       glDepthRange - specify mapping of depth values from normalized device coordinates to window coordinates

C SPECIFICATION
       void glDepthRange( GLclampd zNear,
			  GLclampd zFar )

PARAMETERS
       zNear  Specifies the mapping of the near clipping plane to window coordinates.  The initial value is 0.

       zFar   Specifies the mapping of the far clipping plane to window coordinates.  The initial value is 1.

DESCRIPTION
       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.

NOTES
       It is not necessary that zNear be less than zFar.  Reverse mappings such as zNear=1, and zFar=0 are acceptable.

ERRORS
       GL_INVALID_OPERATION is generated if glDepthRange is executed between the execution of glBegin and the corresponding execution of glEnd.

ASSOCIATED GETS
       glGet with argument GL_DEPTH_RANGE

SEE ALSO
       glDepthFunc, glPolygonOffset, glViewport

																  GLDEPTHRANGE(3G)