I’m planning a texture paging system, and I want to try a method detailed on this SGI page . It uses a single texture object updated with glTexSubImage. This requires updating smaller regions of the texture. My question concerns the performance of glTexSubImage on modern hardware ( >= TNT), specifically when updating narrow regions of texture. Do cards upload entire scanlines even if only a small part of them are updated? Do they perform worse when using GL_SKIP_PIXELS and/or GL_SKIP_ROWS? Are there alignment issues, or some kind of minimum granularity (like 4x4 blocks)?