Methods of rendering an object-based image are described. The methods receive a list of objects (951-955) in the image (950), the list ordering the objects in priority order from a lowest-priority object (951) to a highest-priority object (955). The objects are assigned to a first set of objects (951, 952) and/or a second set of objects (953-955). The first set of objects is rendered to an image store using a first rendering method that only renders a portion of an object if the portion is visible in the first set of objects and the second set of objects is rendered to the image store using a second rendering method that renders each object independently of the other objects in the second set. The assignment may be based on a priority order of a highest-compositing object (952). The assignment may be based on a group of overlapping objects (1101, 1102, 1103, 1105), where an object (1105) in the group requires compositing.