A medical image processing apparatus comprises processing circuitry configured to: obtain a medical imaging data set representative of at least part of at least one surface; render from the medical imaging data set at least one image of the at least part of the at least one surface, wherein the or each image is rendered using a respective lighting configuration; and determine a measure of lighting quality for the or each rendered image; wherein, for the or each rendered image, the determining of the measure of lighting quality comprises, for each of a plurality of locations on the at least part of the at least one surface, determine a correspondence between a curvature of the at least one surface at that location and a lighting value at that location, wherein the lighting value is obtained from the rendering of the image; and determine the measure of lighting quality based on the determined correspondences.