Judging by examples, docs, sources etc. osg::Camera handles multiple jobs: render target (attaching to render buffer in case of RTT), viewport and view/projection transformation. Is it possible to somehow split view/projection role into separate camera object, such that it's handled independent of render target and viewport? Maybe some kind of nesting cameras? The only idea I have in mind is to insert two MatrixTransform nodes at the top of scene which will present that role, although I don't like it because it will interfere with local-to-world transformations in some cases.