control the front and/or back writing of individual bits in the stencil planes
glStencilMaskSeparate controls the writing of individual bits in the stencil planes. The least significant bits of mask , where is the number of bits in the stencil buffer, specify a mask. Where a 1 appears in the mask, it's possible to write to the corresponding bit in the stencil buffer. Where a 0 appears, the corresponding bit is write-protected. Initially, all bits are enabled for writing.
There can be two separate mask writemasks; one affects back-facing polygons, and the other affects front-facing polygons as well as other non-polygon primitives. glStencilMask sets both front and back stencil writemasks to the same values, as if glStencilMaskSeparate were called with face set to GL_FRONT_AND_BACK .
GL_INVALID_ENUM is generated if face is not one of the accepted tokens.
glGet with argument GL_STENCIL_WRITEMASK , GL_STENCIL_BACK_WRITEMASK , or GL_STENCIL_BITS
Copyright 2006 Khronos Group. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. http://opencontent.org/openpub/ .