Tree is a key component in the natural environment, thus modeling trees has been a hot topic in computer graphics. However, trees are not easy to model due to their geometric complexity and great variety. Billboard technique, namely using tree image instead of tree is a common method in virtual scene, but in the close shot, tree image would give bad effect. After thoroughly investigating 3D tree modeling methods, we present a thought of modeling tree's trunk with fractal method based on L system. In order to simplify the modeling process and improve the display speed, our system generates the twigs and leaves with billboard, one billboard represents one twig. By this approach, the result of experiment shows that we can realize the high-speed visualization and vivid effect, so the thought is of reference value.
