A graphics processing apparatus is provided with rendering circuitry which separately renders different areas of a frame of pixel values. Monitoring circuitry coupled to the rendering circuitry captures for each area rendered one or more parameters and stores these parameters to a parameter memory. A performance frame can be generated from the captured and stored parameters with performance-representing pixel values for each area within the performance frame corresponding to an area within the image frame and having a visual characteristic selected in dependence upon the performance parameter which was captured. The visual characteristic may be a grey-scale value, a pixel intensity or a pixel color.