A shadow rendering method for an image includes: re-projecting 3D coordinates of image pixels from an image space of the image to points on a 2D shadowmap space; estimating at least one of a horizontal and vertical distribution of the points in the shadow map space; for a flexible scale rasteriser ‘FSR’, updating a horizontal or vertical FSR curve corresponding to a distribution of FSR bins for the shadow map so that the corresponding horizontal or vertical distribution of points per bin is most even; and rendering the shadow map using flexible scale rasterization.