glDrawBuffer

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Specify which color buffers are to be drawn into.

C Specification[edit]

void glDrawBuffer( GLenum buf );
void glNamedFramebufferDrawBuffer( GLuint framebuffer, GLenum buf );


Parameters[edit]

framebuffer - Specifies the name of the framebuffer object for glNamedFramebufferDrawBuffer function. Must be zero or the name of a framebuffer object.
buf - For default framebuffer, the argument 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. For framebuffer objects, GL_COLOR_ATTACHMENT$m$ and GL_NONE enums are accepted, where $m$ is a value between 0 and GL_MAX_COLOR_ATTACHMENTS .


Description[edit]

When colors are written to the frame buffer, they are written into the color buffers specified by glDrawBuffer . One of the following values can be used for default framebuffer:


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 onlyleftbuffers, and stereoscopic contexts include bothleftandrightbuffers. Likewise, single-buffered contexts include onlyfrontbuffers, and double-buffered contexts include bothfrontandbackbuffers. The context is selected at GL initialization.

For framebuffer objects, GL_COLOR_ATTACHMENT$m$ and GL_NONE enums are accepted, where $m$ is a value between 0 and GL_MAX_COLOR_ATTACHMENTS . glDrawBuffer will set the draw buffer for fragment colors other than zero to GL_NONE .


Errors[edit]

 GL_INVALID_OPERATION error is generated by glNamedFramebufferDrawBuffer if framebuffer is not zero or the name of an existing framebuffer object.

 GL_INVALID_ENUM is generated if buf is not an accepted value.

 GL_INVALID_OPERATION is generated if the default framebuffer is affected and none of the buffers indicated by buf exists.

 GL_INVALID_OPERATION is generated if a framebuffer object is affected and buf is not equal to GL_NONE or GL_COLOR_ATTACHMENT$m$ , where $m$ is a value between 0 and GL_MAX_COLOR_ATTACHMENTS .


Associated Gets[edit]

 glGet with argument GL_DRAW_BUFFER 


Version Support[edit]

 glDrawBuffer  2.0+
 glNamedFramebufferDrawBuffer  4.5+

See Also[edit]

 glBlendFunc , glColorMask , glDrawBuffers , glLogicOp , glReadBuffer 


Copyright[edit]

Copyright© 1991-2006 Silicon Graphics, Inc. Copyright© 2010-2014 Khronos Group. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.