Choosing a good set of occluders can be computationally expensive as it is approximating the task of determining the visible surfaces. Heuristic methods can be used to choose likely occluders based on an estimation of the size of the occluder and distance from they eye. In order to maintain interactive rendering it may be useful to assign a fixed polygon budget to the list of occluders. Temporal coherence can be exploited to reduce the number of new occluders that need to be considered each frame.