Hi, I'm trying to sort of simulate SDL "style" of 2D operations via openGL and don't understand one thing.

I need to draw a rectangular area from one texture to the screen or to another texture.

I've found the glCopyTexImage2D() and glCopyTexSubImage2D() functions but I don't understand one thing. What is the source? I mean, do I have to first draw the source texture somewhere before I can "copy" it ?