View-Dependent Visibility Estimation for Tree Models

A view-dependent visibility estimation technique for tree models is proposed in this work. While most previous work focused on visibility estimation of large objects in architectural walkthroughs, we consider the visibility estimation problem of tree leaves in complex natural scenes such as forests. Exact calculation of how each leaf object blocks another from a given viewpoint is difficult due to the large amount of computational cost. To address this issue, we propose three simple yet effective methods for efficient visibility estimation of tree leaves: the distance-based, the normal-based, and the layer-plus-normal-based methods. Experimental results show that the distance-based method always produces the best analytical performance, the normal-based method works better in preserving volumetric visual quality at low budget constraints, and the layer-plus-normal-based method preserves volumetric visual quality while yielding excellent analytical performance.