Hi, In old graphics cards texture sizes had to be a power of 2. Also FBO didn't exist yet. Is it a relatively precise assumption that I do if I assume that the free texture sizes are not supported if FBO is not supported? or, is there a function which tells me if the graphic card supports free texture sizes (not constrained to be a power of 2)? Right now I can check for FBO and if not present, then I also constain texture sizes to be a power of 2.

Just check for the appropiate extensions. For FBOs, is GL_EXT_framebuffer_object, and for NPOT textures, GL_ARB_texture_non_power_of_two.

Thanks HuntsMan, perfect! :)