GlDrawBuffer

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_glDrawBuffer: specify which color buffers are to be drawn into


Syntax

SUB _glDrawBuffer (BYVAL mode AS _UNSIGNED LONG)
void _glDrawBuffer(GLenum mode);


mode
Specifies up to four color buffers to be drawn into. Symbolic constants _GL_NONE, _GL_FRONT_LEFT, _GL_FRONT_RIGHT, _GL_BACK_LEFT, _GL_BACK_RIGHT, _GL_FRONT, _GL_BACK, _GL_LEFT, _GL_RIGHT, and _GL_FRONT_AND_BACK are accepted. The initial value is _GL_FRONT for single-buffered contexts, and _GL_BACK for double-buffered contexts.


Description

When colors are written to the frame buffer, they are written into the color buffers specified by _glDrawBuffer. The specifications are as follows:

_GL_NONE
No color buffers are written.
_GL_FRONT_LEFT
Only the front left color buffer is written.
_GL_FRONT_RIGHT
Only the front right color buffer is written.
_GL_BACK_LEFT
Only the back left color buffer is written.
_GL_BACK_RIGHT
Only the back right color buffer is written.
_GL_FRONT
Only the front left and front right color buffers are written. If there is no front right color buffer, only the front left color buffer is written.
_GL_BACK
Only the back left and back right color buffers are written. If there is no back right color buffer, only the back left color buffer is written.
_GL_LEFT
Only the front left and back left color buffers are written. If there is no back left color buffer, only the front left color buffer is written.
_GL_RIGHT
Only the front right and back right color buffers are written. If there is no back right color buffer, only the front right color buffer is written.
_GL_FRONT_AND_BACK
All the front and back color buffers (front left, front right, back left, back right) are written. If there are no back color buffers, only the front left and front right color buffers are written. If there are no right color buffers, only the front left and back left color buffers are written. If there are no right or back color buffers, only the front left color buffer is written.

If more than one color buffer is selected for drawing, then blending or logical operations are computed and applied independently for each color buffer and can produce different results in each buffer.

Monoscopic contexts include only left buffers, and stereoscopic contexts include both left and right buffers. Likewise, single-buffered contexts include only front buffers, and double-buffered contexts include both front and back buffers. The context is selected at GL initialization.


Errors

_GL_INVALID_ENUM is generated if mode is not an accepted value.

_GL_INVALID_OPERATION is generated if none of the buffers indicated by mode exists.


Use With:

_glGet with argument _GL_DRAW_BUFFER


See also

_GL _glBindFramebuffer, _glBlendFunc, _glColorMask, _glDrawBuffers, _glLogicOp


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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