1. A method for texturing and shading a 3D computer graphic image on a plurality of shading engines comprising the steps of: subdividing the image into a plurality of rectangular areas; subdividing each rectangular area into a plurality of smaller rectangular areas; allocating an object list to each rectangular area, the object list containing data defining objects visible in the rectangular area; for each smaller rectangular area in turn: determining which pixels in the smaller rectangular area are intersected by a next object from the object list and which pixels in said smaller rectangular area are intersected by a respective next object from the object list used on a previous pixel intersection determination for each respective other smaller rectangular area; outputting pixel intersection data for an object for which all intersection determinations for each of the smaller rectangular areas have been performed to shading engines allocated to each of the respective smaller rectangular areas; texturing and shading the pixels corresponding to the pixel intersection data for the said object with the shading engines; and storing data derived by the texturing and shading step for the pixels corresponding to the pixel intersection data.