glDrawBuffer

glDrawBuffer: man4/glDrawBuffer.xml

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: 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 buffers, and stereoscopic contexts include both and buffers. Likewise, single-buffered contexts include only buffers, and double-buffered contexts include both and buffers. 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.