Résumé
Modeling and rendering of large forest scenes are a challenging task, whose geometric complexity surpasses even the capabilities of current graphics hardware. A tree model simplification tool is developed in this paper to automatically generate both hybrid polygon/image-based tree models for close distance viewing and cross billboards for far distance viewing. In the hybrid model, the foliage of the tree is replaced by a set of arbitrarily oriented billboards while the trunk and branches remains polygon models, so that the 3D perception is enhanced and weak parallax of usual image based approaches is avoided. A fast forest rendering system is also developed. We present techniques in the system for rendering forest consisting of many highly detailed plant models. This forest rendering system allows us to render a large forest scene in real-time. Walk-through and flyover a forest are also simulated, illustrating applications for computer games and interactive visualization of landscapes.