 <p>To hav transparency, you need an alpha channel, on your texture, but more important, in your framebuffer. This is done with SDL_GL_SetAttribute, for example:</p> <pre><code>SDL_GL_SetAttribute( SDL_GL_RED_SIZE, 8 ); SDL_GL_SetAttribute( SDL_GL_GREEN_SIZE, 8 ); SDL_GL_SetAttribute( SDL_GL_BLUE_SIZE, 8 ); SDL_GL_SetAttribute( SDL_GL_ALPHA_SIZE, 8 ); </code></pre> <p>This will request a framebuffer with at least those sizes, and you'll be able to use blending. Remember to enable blending and set a blending function.</p>