glDrawBuffer — specify which color buffers are to be drawn into
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.
When colors are written to the frame buffer, they are written into the color buffers specified by glDrawBuffer. The specifications are as follows:
GL_NONENo color buffers are written.
GL_FRONT_LEFTOnly the front left color buffer is written.
GL_FRONT_RIGHTOnly the front right color buffer is written.
GL_BACK_LEFTOnly the back left color buffer is written.
GL_BACK_RIGHTOnly the back right color buffer is written.
GL_FRONTOnly 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_BACKOnly 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_LEFTOnly 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_RIGHTOnly 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_BACKAll 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.
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.
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