1. A graphics processing apparatus, comprising: a raster stage configured to identify neighboring primitives for concurrent multi-sample processing as coalesced groups each coalesced group comprising adjacent non-overlapping triangles generated from a common surface; and a pixel shader configured to concurrently shade individual coalesced groups with the shading including texture operations to determine the color of pixels within coalesced groups; wherein said pixel shader is configured to evaluate pixel attributes at each multi-sample sample location within a coalesced group to concurrently perform multi-sampling of sample locations within the coalesced group for pixels straddling a common edge between neighboring primitives of said coalesced group and generate a single color while retaining z-data for a plurality of multi-sample locations for each pixel straddling a common edge between neighboring primitives of said coalesced group to perform z-testing.