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GLDEPTHFUNC(3G)                                  OpenGL 3.3                                  GLDEPTHFUNC(3G)



NAME
       glDepthFunc - specify the value used for depth buffer comparisons

C SPECIFICATION
       void glDepthFunc(GLenum func);

PARAMETERS
       func
           Specifies the depth comparison function. Symbolic 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.)


       func 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 func is GL_LESS. Initially, depth testing is disabled. If depth testing is
       disabled or if no depth buffer exists, it is as if the depth test always passes.

NOTES
       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. In order to unconditionally write to the depth buffer, the depth test
       should be enabled and set to GL_ALWAYS.

ERRORS
       GL_INVALID_ENUM is generated if func is not an accepted value.

ASSOCIATED GETS
       glGet() with argument GL_DEPTH_FUNC


       glIsEnabled() with argument GL_DEPTH_TEST

SEE ALSO
       glDepthRange(), glEnable(), glPolygonOffset()


COPYRIGHT
       Copyright (C) 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software
       B License. For details, see http://oss.sgi.com/projects/FreeB/.



OpenGL 3.3                                       03/08/2011                                  GLDEPTHFUNC(3G)