View-dependent multiresolution model for foliage

Real-time rendering of vegetation is one of the most important challenges in outdoor scenes. This is due to the vast amount of polygons that are used to model vegetable species. Multiresolution modeling has been successfully presented as a solution to the problem of efficient manipulation of highly detailed polygonal Surfaces. In order to construct a multiresolution model, a simplification method must be used. The previously introduced Foliage Simplification Algorithm, FSA, obtains different approximations of a tree model. This automatic simplification method diminishes the number of polygons that form the crown while maintaining its leafy appearance. In this paper a multiresolution model for trees based on this simplification algorithm is presented. Its distinctive property is that the unit of information managed by this scheme is the leaf, four vertices determining two triangles. This characteristic allows us an efficient manipulation of the results obtained by FSA. Our multiresolution representation provides a wide, virtually continuous, range of different approximations that represent the original tree. The main property of this scheme is that trees can be represented with variable resolution: some regions in more detail while the rest is represented in less detail. Here we present the data structures and the traversing algorithms, which favor the exit-action of an appropriate level of detail for rendering.