1. An image processing method wherein a location of a face is detected, the method comprising obtaining a 3D surface model from measurements of a scene; generating a 2D image of angle data from the 3D surface model, the 2D image including the angle data, the angle data for each respective image point in the 2D image being an angle between an incidence direction derived from a virtual lighting direction and a normal to the 3D surface at a point on the 3D surface that is in view in the 2D image at the image point or a trigonometric function of the angle; applying a 2D face location algorithm to the 2D image, wherein the 2D face location detection algorithm performs calculations on the angle data.