fglDepthRange(3G)

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


FORTRAN SPECIFICATION
     SUBROUTINE fglDepthRange( REAL*4 near,
                               REAL*4 far )


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

     far   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.  fglDepthRange
     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 fglDepthRange 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 near be less than far.  Reverse mappings such as
     near=1, and far=0 are acceptable.

ERRORS
     GL_INVALID_OPERATION is generated if fglDepthRange is executed between
     the execution of fglBegin and the corresponding execution of fglEnd.

ASSOCIATED GETS
     fglGet with argument GL_DEPTH_RANGE


MACHINE DEPENDENCIES
     Although it is possible to reverse the depth mapping so that near is 1
     and far is 0, doing so may cause severe depth-buffering artifacts on
     InfiniteReality systems.  (This is particularly true for 15-bit depth
     buffers.)  Therefore this practice is strongly discouraged.
SEE ALSO
     fglDepthFunc, fglPolygonOffset, fglViewport