To perform a graphics processing operation for the entirety of an area of a render output being generated by a graphics processor, a command to draw a primitive occupying the entire area of the render output is issued to the graphics processor. The graphics processor draws the primitive by determining the vertices to use for the primitive from the area of the render output. In a tile-based graphics processor at least, the graphics processor in an embodiment also determines whether it is unnecessary to process the graphics processing command for a rendering tile and when it is determined that processing the graphics processing command for the rendering tile is unnecessary, the graphics processor omits processing the graphics processing command for the rendering tile.