A system of processing of three dimensional [3D] image data for display on a 3D display for a viewer is described. 3D display metadata defines spatial display parameters of the 3D display such as depth range supported by the 3D display. Viewer metadata defines spatial viewing parameters of the viewer with respect to the 3D display, such as viewing distance or inter-pupil distance. Source 3D image data arranged for a source spatial viewing configuration is processed to generate target 3D display data for display on the 3D display in a target spatial viewing configuration. First the target spatial configuration is determined in dependence of the 3D display metadata and the viewer metadata. Then, the source 3D image data is converted to the target 3D display data based on differences between the source spatial viewing configuration and the target spatial viewing configuration.