I created a 2D demo a while ago. It was pretty simple with just a sprite walking around. To make him transparent, I had to use a seperate sprite map that was black. I am assuming this is called masking. I got use to DirectDraw/Direct3D's way of doing 2D. There was no "seperate image," as it was an offscreen surface. I would just tell it not to blit a certain color to the back buffer. It did the trick. Is there anything like that in OpenGL? I'd hate having two seperate images just in hope for transparency purposes.