lsetde(3G)

NAME
     lsetde - sets the depth range

FORTRAN SPECIFICATION
     subroutine lsetde(near, far)
     integer*4 near, far

PARAMETERS
     near   expects the screen coordinate of the near clipping plane.

     far    expects the screen coordinate of the far clipping plane.

DESCRIPTION
     viewpo specifies the mapping of the left, right, bottom, and top clipping
     planes into screen coordinates.  lsetde completes this mapping for
     homogeneous world coordinates; it specifies the mapping of the near and
     far clipping planes into values stored in the z-buffer.

     lsetde is used in z-buffering, depth-cueing, and certain feedback
     applications.

     The valid range of the parameters depends on the state of the GLCZRA
     compatibility mode (see glcomp).  If it is 0, the valid range depends on
     the graphics hardware.  When multisample is enabled, and multisample
     buffers exist in the current framebuffer configuration in the current
     drawmode, the minimum is the value returned by getgco(GCMZMI) and the
     maximum is the value returned by getgco(GCMZMA).  Otherwise, the minimum
     is the value returned by getgco(GCZMIN) and the maximum is the value
     returned by getgco(GCZMAX).  If the state of the GLCZRA compatibility
     mode is 1, the minimum is $0 and the maximum is $7FFFFF.  The depth range
     defaults to the full range supported by the graphics hardware.

     Acceptable mappings include all those where both near and far are within
     the supported range, including mappings where near > far.  In particular,
     it is sometimes desirable to call lsetde($7FFFFF, $0) on IRIS-4D GT and
     GTX models.

SEE ALSO
     depthc, feedba, getgde, glcomp, zbuffe

NOTES
     Error accumulation in the iteration of z can cause wrapping when the full
     depth range supported by the graphics hardware is used.  (An iteration
     wraps when it accidentally converts an large positive value into a
     negative value, or vice versa.)  While the effects of wrapping are
     typically not observed, if they are, they can be eliminated by reducing
     the depth range by a small percentage.

     When using this routine, you should always explicitly set the GLCZRA mode
     of glcomp because its default is different on different models.