Parameters mode Specifies up to four color buffers to be drawn into.
When colors are written to the frame buffer, they are written into the color buffers specified by glDrawBuffer . Only the front left color buffer is written. If there is no front right color buffer, only the front left color buffer is written. If there is no back right color buffer, only the back left color buffer is written. If there is no back left color buffer, only the front left color buffer is written.