Tight Conservative Occlusion Culling for Urban

In this paper, we propose a framework for the visualization of urban environments. In this context, we also propose a novel tight conservative occlusion culling algorithm, which brings a solution to the partial occlusion problem. A conservative visibility culling algorithm accepts an object as completely visible even only a small portion of it is unoccluded. In our algorithm, we tried to avoid this by decomposing the objects into slices to achieve tight conservativeness. This sliced structure is queried for visibility at prede ned grid locations in the scene. Since the slices of objects are checked for visibility instead of complete objects, only a very small portion of polygons of an object are sent to the graphics pipeline unnecessarily if a small portion of the object is unoccluded. The grid cells with approximately the same visibility lists are clustered to decrease the size of the visibility information that will be used during the visualization process. Empirical results show that an average speed up of 41 % can be achieved using our tight conservative occlusion culling algorithm as compared to the classical conservative occlusion culling approach