A Hybrid Geometry and Billboard-Based Model for Trees

Many applications, such as games, demand massive collections of trees and vegetation in general. The solutions for rendering these environments fall into two possible categories: controlling the amount of geometry displayed, and billboard-based solutions. Using the full geometry is prohibitively expensive when dense forests are needed, therefore level-of-detail solutions are commonly used to reduce the amount of polygons in the scene, however demanding more processing or increased texture memory usage. On the other hand, dynamic billboards rely on render-to-texture operations, which are also costly. We describe an alternative hybrid solution that does not use full geometry, but instead builds trees from textured billboards and simple geometry. By using a simple rule-based L-system and a small set of textures, we can achieve realistically looking visual results of dense vegetation adequate for close to far distance viewing. Our approach provides controlled tree variability and employs fewer polygons than current techniques.