Generation, Renderingand Animation of Polygon Tree Models

This thesis contains a set of contributions that focuses on challenges in visualization of polygon models of trees, in particular models of tree stems and branches. These challenges cover a wide range of the visualization research field, including generation of polygon models of trees, hardware accelerated visualization and animation of trees from parametric systems, and surface modelling and tessellation for tree stems. To generate polygon models of trees, an existing approach for automatically generating polygon models of branching vascular transportation systems, typically blood vessels, is extended to handle tree stems. The approach allowed for automation of the generation process, while maintaining smoothness at branching areas. The approach is used to generate polygon models of trees. For hardware accelerated visualization and animation of trees from parametric systems, methods for visualization of trees described by parametric descriptions are adapted and extended to run on dedicated graphic processing hardware. To allow for animation of trees visualized in such a manner, an animation process that is hardware accelerated is developed using knowledge gained from work on hardware acceleration approaches in the field of image processing. For surface modelling and tessellation for visualization of trees, concepts, ideas and early work are presented. The basic concept is that by working with a coarse polygon model of a tree during animation (or by generating a coarse polygon model of a tree after animation is done); one can tessellate this coarse model in hardware in real-time to a much higher degree then earlier approaches. This will then enable one to visualize trees stems of a higher Level of Detail (LOD) and at higher speeds than were previously achievable. Although the contributions in this thesis cover a wide range of challenges from the visualization research field, the main focus has been on generation, animation and visualization of tree stems and branches for use in real-time applications. Especially the concept of hardware acceleration has become more of a focus, as graphic processing hardware has become more and more powerful both in speed and especially in functionality. The contributions will hopefully help in future development of even better methods for visualizing trees and plants.