Difference between revisions of "GlDepthFunc"

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(Created page with ''''_glDepthFunc:''' specify the value used for depth buffer comparisons {{PageSyntax}} SUB _glDepthFunc (BYVAL func AS _UNSIGNED LONG) void '''_glDepthFunc'''(GLenum {{Par…')
 
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{{PageCopyright}}
 
{{PageCopyright}}
 
Copyright 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/ http://oss.sgi.com/projects/FreeB/].
 

Revision as of 15:16, 25 August 2013

_glDepthFunc: specify the value used for depth buffer comparisons


Syntax

 SUB _glDepthFunc (BYVAL func AS _UNSIGNED LONG)
 void _glDepthFunc(GLenum func);


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.


Use With:

_glGet with argument _GL_DEPTH_FUNC

_glIsEnabled with argument _GL_DEPTH_TEST


See also

_GL (GL_DEPTH_TEST), _glDepthRange, _glPolygonOffset


Copyright: 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/.



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