When generating a graphics processing output, a sequence of one or more of primitives to be processed when generating the output is assembled from a set of vertex indices provided for the output based on primitive configuration information provided for the output, each assembled primitive of the sequence of assembled primitives comprising an identifier for the primitive and a set of one or more vertex indices for the primitive. One or more attributes for vertices of the assembled primitives are then shaded and fetched based on the vertex indices of the assembled primitives. The assembled primitives including their shaded fetched vertex attribute(s) are then provided to later stages of the graphics processing pipeline for processing.