GlDepthFunc
_glDepthFunc: specify the value used for depth buffer comparisons
Contents
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
SUB _GL (GL_DEPTH_TEST), _glDepthRange, _glPolygonOffset
