【作者】 张佳佳；

【导师】 淮永建；

【作者基本信息】 北京林业大学 ， 计算机应用技术， 2010， 硕士

【摘要】 树木的模拟是计算机图形学在林学可视化领域应用的前沿课题之一,树木的形态结构在其生长过程中起着重要的作用,在树几何建模的过程中,真实地模拟树木枝条的自然弯曲状态是一个重要的因素。论文主要研究了树木可视化建模和树木可视化场景建模两个部分。树木建模采用分形理论的迭代函数系统来完成,建模时着重实现了以参数化曲线拟合的方法来模拟枝条的自然弯曲状态。通过引进Bezier:这种基于控制点的自由曲线来拟合枝条曲线,并将枝条定义为以Bezier曲线为轴、横截面直径变化的广义圆柱体。在可视化场景的建模中,对地形生成算法进行了研究,采用随机中点位移法中的"diamond-square"算法实现了分形地形的模拟,建立了一个三维虚拟场景。实验结果表明,相较于以往用圆柱或圆台绘制的树的枝干,本文所采用的基于控制点变化的Bezier曲线能较好地模拟枝条自然弯曲和光滑连续的状态,构建的树模型能更好地反映真实树木的形态特征。更多还原

【Abstract】 The simulation of trees is one of the leading issues of computer graphics in the field of forestry visualization applications. The morphology of trees plays an important part in their growth. In the process of tree geometry modeling, the simulation of tree branches’bending state is very important. The paper includes the tree modeling and the virtual scene building. Tree modeling uses the iterated function system based on fractal theory. The parameterized curve is used to simulate the bending state of tree branches. Bezier curve, a free curve based on controlled points, is used to simulate dynamic of the branch axis curve. Generalized cylinder, a three-dimensional with Bezier curve as the axis, is used to define the branch. In the visualization of scene, the "diamond-square" algorithm based on random midpoint displacement is used to simulate the fractal terrain. As a result, a three-dimensional virtual scene is built. Experiments show that, compared to previous branches simulated by cylinder, Bezier curve can simulate the bending and smooth state of branches better. The tree model better reflects the true characteristics of real tree.更多还原