According to another aspect of the invention there is provided a computer system for rendering an image
comprising at least one light source, a first shadow-casting object with a second shadow-receiving object located on
the side of the first shadow-casting object remote from said at least one light source, the computer system comprising:
a shadow mask memory in which is stored a shadow mask which identifies for each of a plurality of pixels on the
shadow receiving object a grey level representing the intensity of shadow in each pixel, the intensity having been
determined utilising the distance between the shadow-casting object and the shadow-receiving object; and processing
means for utilising the shadow mask to render the image by adjusting the texture of each pixel based on said grey
level representing the intensity of shadow.