The Global Occlusion Map: a New Occlusion Culling Approach

Occlusion culling is an important technique to speed up the rendering process for walkthroughs in a complex environment. In this paper, we present a new approach for occlusion culling with respect to a view cell. A compact representation, the Global Occlusion Map (GOM), is proposed for storing the global visibility information of general 3D models with respect to the view cell. The GOM provides a collection of Directional Visibility Barriers (DVB), which are virtual occluding planes aligned with the main axes of the world coordinates that act as occluders to reject invisible objects lying behind them in every direction from a view cell. Since the GOM is a two-dimensional array, its size is bounded, depending only on the number of the sampled viewing directions. Furthermore, it is easy to conservatively compress the GOM by treating it as a depth image. Due to the axial orientations of the DVBs, both the computational and storage costs for occlusion culling based on the GOM is minimized. Our implementation shows the Global Occlusion Map is effective and efficient in urban walkthrough applications.