Framebuffer objects in Cinder (by default) have no anti-aliasing which leaves your edges jagged.
The solution is to create a Framebuffer format and specify the number of samples to use.
gl::Fbo::Format msaaFormat; msaaFormat.setSamples( 4 ); // enable 4x MSAA gl::Fbo myMsaaFbo( 640, 480, msaaFormat );