1. A computer program product, comprising: a computer-readable medium; computer program instructions stored on the computer readable medium that when processed by a computer instruct the computer to define a processor, comprising: a vertex shader having an output for providing output data generated for a vertex in a mesh; a fragment shader having an input for receiving input data corresponding to the output data from the vertex shader, from which the fragment shader can determine original values for each vertex defining a primitive containing a fragment being processed by the fragment shader.