3.1 KiB
_glReadBuffer: select a color buffer source for pixel read operations from the current read framebuffer.
Syntax
SUB _glReadBuffer (BYVAL mode AS _UNSIGNED LONG) void _glReadBuffer(GLenum mode);
; mode
Specifies a color buffer. Accepted values are _GL_FRONT_LEFT, _GL_FRONT_RIGHT, _GL_BACK_LEFT, _GL_BACK_RIGHT, _GL_FRONT, _GL_BACK, _GL_LEFT, _GL_RIGHT, and the constants _GL_COLOR_ATTACHMENTi.
Description
_glReadBuffer specifies which color buffer within the current bound _GL_READ_FRAMEBUFFER will be used as the source for pixel reading commands. These commands include: _glBlitFramebuffer, _glReadPixels, _glCopyTexImage1D, _glCopyTexImage2D, _glCopyTexSubImage1D, _glCopyTexSubImage2D, and _glCopyTexSubImage3D.
mode accepts one of twelve or more predefined values. If the [default framebuffer](default framebuffer) (the zero [framebuffer object](framebuffer object))is bound to _GL_READ_FRAMEBUFFER, then the following enumerators can be used: _GL_FRONT, _GL_LEFT, and _GL_FRONT_LEFT all name the front left buffer, _GL_FRONT_RIGHT and _GL_RIGHT name the front right buffer, and _GL_BACK_LEFT and _GL_BACK name the back left buffer. Nonstereo double-buffered configurations have only a front left and a back left buffer. Single-buffered configurations have a front left and a front right buffer if stereo, and only a front left buffer if nonstereo.
If a non-zero framebuffer object is bound, then the constants _GL_COLOR_ATTACHMENTi may be used to indicate the ith color attachment, where i ranges from zero to the value of _GL_MAX_COLOR_ATTACHMENTS minus one.
It is an error to specify a nonexistent buffer to _glReadBuffer.
For the default framebuffer, mode is initially _GL_FRONT in single-buffered configurations and _GL_BACK in double-buffered configurations. For framebuffer objects, the default read buffer is _GL_COLOR_ATTACHMENT0.
Error(s)
_GL_INVALID_ENUM is generated if mode is not one of the twelve (or more) accepted values.
_GL_INVALID_OPERATION is generated if mode specifies a buffer that does not exist.
Use With
_glGet with argument _GL_READ_BUFFER
See Also
_GL _glBindFramebuffer, _glDrawBuffer, _glDrawBuffers, _glReadPixels
Copyright 1991-2006 Silicon Graphics, Inc. Copyright 2011 Khronos Group. 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/].