I have the following problem I appreciate some help with:

I render everything in a multisampled renderbuffer of a framebuffer then blit the result to a ‘normal’ renderbuffer (GL_COLOR_ATTACHMENT0_EXT) of another framebuffer. Then I read back this finished buffer (I need to process it in system RAM). But as a preview I would also like to display it in a window.

I have a rendering context and I thought I should copy the contents of the renderbuffer to the its back buffer (GL_BACK) using CopyPixels. However it does not work (I get nothing) and I have no idea why. The renderbuffer has the finished image because I can read it back and save it to disk.

Your thoughts would be appreciated.