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