-  control  the  writing  of  individual bits in the color
       index buffers



C SPECIFICATION


PARAMETERS

       _param1  Specifies a bit mask to enable  and  disable  the
                writing  of  individual  bits  in the color index
                buffers.  Initially, the mask is all 1's.


DESCRIPTION

       glIndexMask controls the writing of individual bits in the
       color  index  buffers.   The  least  significant n bits of
       _param1, where n is the number of bits in  a  color  index
       buffer,  specify  a  mask.  Where a 1 (one) appears in the
       mask, it's possible to write to the corresponding  bit  in
       the  color  index  buffer  (or buffers).  Where a 0 (zero)
       appears, the corresponding bit is write-protected.

       This mask is used only in color index mode, and it affects
       only  the  buffers  currently  selected  for  writing (see
       glDrawBuffer).  Initially, all bits are enabled for  writ-
       ing.


ERRORS

       GL_INVALID_OPERATION  is  generated if glIndexMask is exe-
       cuted between the execution of glBegin and the correspond-
       ing execution of glEnd.


ASSOCIATED GETS

       glGet with argument GL_INDEX_WRITEMASK


SEE ALSO

       glColorMask,     glDepthMask,    glDrawBuffer,    glIndex,
       glIndexPointer, glStencilMask



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