1. A method of determining the total ambient occlusion (AO) at a vertex of an object within a frame comprising the steps of: receiving a signal to produce an image, the image to contain a first object; determining the location of a vertex of the first object; determining a global AO at the vertex of the first object using a first technique; determining a local AO at the vertex of the first object using a second technique; determining a total AO at the vertex of the first object as a function of the local AO and global AO; and, producing the image, the shading at the vertex of the first object to be dependent on the total AO.