1. A method for compressing a list of primitives in a computer graphics system, the method comprising: storing, in a buffer, domain point indices for a first primitive in a list of primitives defining a tessellated patch of surface data; storing, in the buffer, a predicted domain point index for use in compressing one or more subsequent primitives in the list of primitives; comparing domain point indices of a next primitive in the list with the domain point indices stored in the buffer to determine buffer positions of matching indices; repeating, for primitives in the list of primitives, the storing a predicted domain point index and the comparing domain point indices; determining a repeating pattern in the buffer positions of respective matching indices over a sequence of primitives in the list of primitives; and producing compressed domain point indices of the primitives in the sequence by specifying: (i) the pattern in the buffer positions of the matching indices, and (ii) the number of times that the pattern is repeated.