Abstract: The method of producing an image data file representative of a rendered three dimensional image includes the steps of: creating a master image data file representative of a three-dimensional master image which is rendered with contrasting colours for each different object type in the image; creating a plurality of fully rendered image data files representative of the three-dimensional image rendered with realistic surfaces including effects such as shadowing, textures and/or realistic colours; creating a mapping file which records which realistic surfaces are used for different objects types in which fully rendered image data file and which records which contrasting colour is used in the master image data file for each respective object type; selecting a object type realistic surfaces for each object type; processing the master image data file to determine edges of object types in the three dimensional image using the contrasting colour information in the mapping file and an edge detection process, to produce