Eliminate a color channel when rendering an object in OpenGL

Question

Am wondering how to eliminate the red channel when rendering some objects in OpenGL.

I can do this easily using a fragment shader but unfortunately I can't use shaders for this particular project.

Disable the red channel
DrawOject();
Enable the red channel

Is there any solution for this?

Answer 1

You can control which channels are written to the framebuffer by using glColorMask. In your case:

glColorMask(GL_FALSE, GL_TRUE, GL_TRUE, GL_TRUE);

Answer 2

glColorMask(GL_FALSE, GL_TRUE, GL_TRUE, GL_TRUE);