GlClear

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_glClear: clear buffers to preset values


Syntax

SUB _glClear (BYVAL mask AS _UNSIGNED LONG)
void _glClear(GLbitfield mask);


Parameters


Description

  • _glClear sets the bitplane area of the window to values previously selected by _glClearColor, glClearDepth, and _glClearStencil.
  • Multiple color buffers can be cleared simultaneously by selecting more than one buffer at a time using _glDrawBuffer.
  • The pixel ownership test, the scissor test, dithering, and the buffer writemasks affect the operation of _glClear. The scissor box bounds the cleared region. Alpha function, blend function, logical operation, stenciling, texture mapping, and depth-buffering are ignored by _glClear.
  • _glClear takes a single argument that is the bitwise OR of several values indicating which buffer is to be cleared. The values are as follows:
_GL_COLOR_BUFFER_BIT: Indicates the buffers currently enabled for color writing.
_GL_DEPTH_BUFFER_BIT: Indicates the depth buffer.
_GL_STENCIL_BUFFER_BIT: Indicates the stencil buffer.
  • The value to which each buffer is cleared depends on the setting of the clear value for that buffer.


Notes:

If a buffer is not present, then a _glClear directed at that buffer has no effect.


Errors

_GL_INVALID_VALUE is generated if any bit other than the three defined bits is set in mask.


Use With:

_glGet with argument _GL_DEPTH_CLEAR_VALUE

_glGet with argument _GL_COLOR_CLEAR_VALUE

_glGet with argument _GL_STENCIL_CLEAR_VALUE


See also


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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