A medical image data processing system comprising processing circuitry configured to receive three-dimensional medical imaging data； and process the three-dimensional medical imaging data to generate using a virtual light source an image for display, wherein the processing circuitry is configured to vary at least one parameter relevant to the virtual light source in dependence on at least one of a position of a medical device inserted into a human or animal body, a position of a viewing point for virtual endoscopic imaging, and the progress of a procedure.
