1. A method of generating a set of polygon vertices over a region of a three-dimensional object in a graphics processing pipeline, the method comprising: determining, based on meta-information representative of the surface relief of the region of the three-dimensional object, whether to generate a set of polygon vertices over the region of the three-dimensional object; generating the set of polygon vertices over the region of the three-dimensional object, when this is determined to be required; and setting the positions of one or more vertices in the set of polygon vertices based on information representative of the surface relief of the region of the three-dimensional object.