The third approach frequently combines both object and image-space computations. This approach employs depth for sorting or reordering of surfaces. They compare the depth of overlapping surfaces and specify one i.e. closer to the view-plane. The processes in this category use also image-space for conducting visibility type tests.
Area-subdivision method is fundamentally an image-space method although uses object-space calculations for re-ordering of surfaces as per to depth. The method makes utilization of area coherence in a scene through collecting those areas which form part of a particular surface. In this type method, we successively subdivide the whole viewing area in small rectangles till each small area is the projection of part of a particular visible surface or no surface at all.