You may want to switch between normal and reverse perspective. For example when you render left atrium as an image overlay on fluroscopy images then you want to be able to render the front and the back surface of the atrium. Rendering the back side is easy with the regular camera, but to render the front surface (that is closer to the X-ray source) you need reverse perspective.
The good news is that you can very easily achieve reverse perspective in VTK: you just need to invert the sign of a single value in the the projection matrix (as I remember it was the bottom-right value, but maybe it was the one above it). vtkCamera does not have an API for this, but you can modify or subclass it and add the reverse perspective option.
I have implemented this in VTK many years ago and it worked perfectly for both surface and volume rendering. If you find that this technique works well then it would be nice if you could submit a merge request that adds reverse perspective option to vtkCamera, as this is a basic need for all 3D fluroscopy overlay applications.