A method of mapping a virtual environment comprises obtaining a first sequence of video images output by a videogame title; obtaining a corresponding sequence of in-game virtual camera positions at which the video images were created; obtaining a corresponding sequence of depth buffer values for a depth buffer used by the videogame whilst creating the video images; and for each of a plurality of video images and corresponding depth buffer values of the obtained sequences, obtain mapping points corresponding to a sampling distribution of points over the area of a respective video image and their associated depth values; wherein respective mapping points are obtained by projecting co-ordinated derived from the sample points from the video image and associated depth values back into a 3D game world co-ordinate system of the videogame title; thereby obtaining a point cloud dataset of mapping points corresponding to the first sequence of video images.