glDrawBuffer - specify which color buffers are to be drawn
into

glDrawBuffer
	glDrawBuffer(mode) -> None

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, GL_FRONT_AND_BACK, and
      GL_AUXi, where i is between 0 and ``GL_AUX_BUFFERS''
      -1, are	accepted (GL_AUX_BUFFERS is not	the upper
      limit; use glGet to query the number of	available aux
      buffers.)  The initial value is	GL_FRONT for single-
      buffered contexts, and GL_BACK for double-buffered
      contexts.

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.

GL_AUXi		   Only	auxiliary color	buffer i 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.

It is	always the case	that GL_AUXi = GL_AUX0 + i.

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.

GL_INVALID_OPERATION is generated if glDrawBuffer is
executed between the execution of glBegin and	the
corresponding	execution of glEnd.

glGet	with argument GL_DRAW_BUFFER
glGet	with argument GL_AUX_BUFFERS

glBlendFunc, glColorMask, glIndexMask, glLogicOp,
glReadBuffer