I am trying to do some post processing on my 3d scene. When I render directly to the screen edges are sharp, however when I render my scene to an offscreen FBO then render that to a texture that is then drawn to the screen I get strange Z-fighting around object edges. Any Idea how this can be resolved?

The resolution of the FBO image seems to be worse in some places too, however the FBO size is set to the window width and height.

Thanks!

Direct Rendering

FBO rendering