My buddy Google who’s usually most helpful proved to be really bitchy in this matter. But after long arguments with Google I finally got some interesting sources.

This is nothing new, this is nothing revolutionary… this is meant for people with a similar problem as the one I had and help them to find their way to the solution a little quicker than I did.

The standard example for using a Framebuffer Object to render to a texture (for more details and explanations ckeck the FBO 101):

// depth buffer
glGenRenderbuffersEXT(1, &depthBuffer);
glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, depthBuffer);
glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT, width, height);

// create fbo and attach depth buffer
glGenFramebuffersEXT(1, &fbo);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, depthBuffer);

// create texture
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
// set your texture parameters here if required ...

// attach texture
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, texture, 0);

...

// rendering procedure
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
glPushAttrib(GL_VIEWPORT_BIT);
glViewport(0, 0, width, height);
// ... draw ...
glPopAttrib();
// you have to unbind all fbos before you can render to the main window
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);

Now we extend the previous example a little bit by using GL_EXT_framebuffer_multisample and GL_EXT_framebuffer_blit in addition to the GL_EXT_framebuffer_object extension so that we can use multisampling for anti-aliasing. The only tricky part is that we now use two FBOs. One is a normal FBO which also the texture is attached to. Only the second FBO is multisampled. While rendering, the multisampled FBO’s content is blitted to the normal FBO.

// multi sampled color buffer
glGenRenderbuffersEXT(1, &colorBuffer);
glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, colorBuffer);
glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER_EXT, samples, GL_RGBA8, width, height);

// multi sampled depth buffer
glGenRenderbuffersEXT(1, &depthBuffer);
glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, depthBuffer);
glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER_EXT, samples, GL_DEPTH_COMPONENT, width, height);

// create fbo for multi sampled content and attach depth and color buffers to it
glGenFramebuffersEXT(1, &mfbo);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, mfbo);
glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_RENDERBUFFER_EXT, colorBuffer);
glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, depthBuffer);

// create texture
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
// set your texture parameters here if required ...

// create final fbo and attach texture to it
glGenFramebuffersEXT(1, &fbo);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, texture, 0);

...

// rendering procedure
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, mfbo);
glPushAttrib(GL_VIEWPORT_BIT);
glViewport(0, 0, width, height);
// ... draw ...
glPopAttrib();
glBindFramebufferEXT(GL_READ_FRAMEBUFFER_EXT, mfbo);
glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER_EXT, fbo);
glBlitFramebufferEXT(0, 0, width, height, 0, 0, width, height, GL_COLOR_BUFFER_BIT, GL_NEAREST);
// you have to unbind all fbos before you can render to the main window
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
...

// cleaning up
glDeleteRenderbuffersEXT(1, &depthBuffer);
glDeleteRenderbuffersEXT(1, &colorBuffer);
glDeleteFramebuffersEXT(1, &mfbo);
glDeleteFramebuffersEXT(1, &fbo);

Make sure that your graphics device supports the GL_EXT_framebuffer_multisample and GL_EXT_framebuffer_blit extensions because usually if an extension is not available the compiler won’t complain and no error message will be displayed. Instead your application will simply crash (at least this is what happens when you access the OpenGL extensions through glew). If you’re using glew you can simply do such a check by calling glewIsSupported(…). It took me a while to figure out that it was my laptop’s ATI Mobility Radeon X1400 inability to anti-alias a FBO and not my inattention that caused the crash .

One last hint: If you want to render your FBO onto a non-power-of-two sized texture you might be better off using the GL_ARB_texture_rectangle extension. Replace GL_TEXTURE_2D with GL_TEXTURE_RECTANGLE_ARB… that’s it.

Enough extensions, happy hacking!

Update:
Also see http://www.opengl.org/wiki/GL_EXT_framebuffer_multisample