- specify the value used for depth buffer comparisons



C SPECIFICATION


PARAMETERS

       _param1  Specifies  the  depth  comparison function.  Sym-
                bolic  constants  GL_NEVER,  GL_LESS,   GL_EQUAL,
                GL_LEQUAL,  GL_GREATER,  GL_NOTEQUAL,  GL_GEQUAL,
                and GL_ALWAYS are accepted.  The initial value is
                GL_LESS.


DESCRIPTION

       glDepthFunc  specifies  the  function used to compare each
       incoming pixel depth value with the depth value present in
       the  depth  buffer.   The  comparison is performed only if
       depth testing is enabled.  (See glEnable and glDisable  of
       GL_DEPTH_TEST.)

       _param1  specifies  the  conditions  under which the pixel
       will be drawn.  The comparison functions are as follows:

       GL_NEVER        Never passes.

       GL_LESS         Passes if the incoming depth value is less
                       than the stored depth value.

       GL_EQUAL        Passes  if  the  incoming  depth  value is
                       equal to the stored depth value.

       GL_LEQUAL       Passes if the incoming depth value is less
                       than or equal to the stored depth value.

       GL_GREATER      Passes  if  the  incoming  depth  value is
                       greater than the stored depth value.

       GL_NOTEQUAL     Passes if the incoming depth value is  not
                       equal to the stored depth value.

       GL_GEQUAL       Passes  if  the  incoming  depth  value is
                       greater than or equal to the stored  depth
                       value.

       GL_ALWAYS       Always passes.

       The initial value of _param1 is GL_LESS.  Initially, depth
       testing is disabled.  Even if the depth buffer exists  and
       the  depth  mask  is  non-zero,  the  depth  buffer is not
       updated if the depth test is disabled.


ERRORS

       GL_INVALID_ENUM is generated if _param1 is not an accepted
       value.
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