Research On Generation Of Virtual Forest Environments Based On The Law Of Stand Growth

The forest dynamic changes have two distinct characters because of arbor's big shape and its long life-span. One is long time scale, the other is large space scale. The two characters just make forestry research more difficult. In Virtual Forest Environments, complex forest objects are constructed, the laws of stand growth are presented and analyzed with computer graphics technology and forestry knowledge. So Virtual Forest Environments can provide a new way for forestry research due to its character of trying to exceed the limit of time and space. Generating Virtual Forest Environments aims to let forest governors and researchers manage and study forestry more conveniently and efficiently. What forest governors concern about is the fall of arboreal which is relevant to the basic parameters such as diameter at breast height, height of tree and so on. Moreover, they also concern about the competition relationship of trees in spatial configuration which relates to trees' position, height, diameter at breast height, crown width, crown length. Forest stand is the least unit of forest partitions, which inner characteristics are same and distinguished markedly from neighboring sections. In this dissertation these characteristic information in forest stand refer to forest spatial data that is one of parameters of modeling three-dimensional tree model and basic data source of generating Virtual Forest Environments. Reviewing the techniques of surveying forest resource inventory, those forest spatial data can not be obtained conveniently and efficiently just with the remote sensing and ground measurement. Modeling tree with computer has been the popular research issue the domestic and international scholars are interested in. At present, in modeling three-dimensional trees there are L system, iterated function system, diffusion limited aggregation, particle system and interactive modeling. The computing process is complex and amount of calculation is great as trees are modeled trees with these methods. As for visualization system which needs to interact with scene that includes great amount of data, the running speed of system will be influenced when tree's models are imported in scene. Nowadays, there are just few researches about the whole simulating process of the virtual forest growth such as which trees in different shapes are in forest, how to place three-dimensional geometric model of tree into forest scene, how to render realistic Virtual Forest Environments, what will happen in forest after a few years, especially how to apply the practical law of stand growth to Virtual Forest Environments.Therefore, two key problems about generating Virtual Forest Environments which are true of the law of stand growth should be resolved in this dissertation. One is to analyze and simulate forest spatial data, namely not only to describe the present characters of tree in stand, but also to research on how forest spatial data change with time. The other is to construct three-dimensional geometric model of tree and to render forest with modeling and rendering technology of computer graphics ifthe forest spatial data are given, finally to generate a virtual forest which can recur to the past, represent the present, and forecast the future. Research in this dissertation is subsidized by national important foundation research project named "Research On Distributed Virtual Geographic Environments And Modeling Forest By Remote Sensing " that Spatial Information Research Center of Fujian province takes on. Based on existing forest resource and forest growth model in south, the idea of constructing Virtual Forest Environments which are true of the law of stand growth are expounded, and the detailed implementing techniques and methods are put forward. The main research contents of the dissertation are as below:1. Analysis and simulation of the present forest spatial data. The whole-to-individual method based on the law of stand structure is introduced and discussed in order that the individual, namely the present forest spatial da...