林木多样性模型及生长模拟

林木生存环境复杂多变,导致林木形态千差万别,为了准确描述林木的形态多样性特征,提出了一种基于模型分解的林木生长模拟方法。首先构建多样性林木三维模型,使用林木形态的实际测量数据,基于B样条函数约束树干、树冠形态,依据削度方程模拟树干直径的变化趋势,利用Direct3D实现林木形态的三维建模;其次,按林木形态特征进行林木模型分解,将林木模型分为9个子模型;最后,使用场景节点按照拓扑结构关系对子模型进行动态组织,基于胸径、树高、枝下高、冠高和冠幅生长模型,使用多核CPU多线程并行的计算方式,获得各年龄阶段林木东、南、西、北方向形态参数,从而对子模型生长状态进行控制,实现林木不同方向生长变化的可视化模拟。结果表明：该方法可将林木三维模型与生长模型紧密结合起来,林木各方向的枝下高、冠高和冠幅严格按照生长模型进行生长,可有效模拟出林木各方向生长状态的多样性;三维场景渲染帧率（FPS）保持在25以上,平均FPS可以达到50,实现林木生长的方向异质性模拟。

Diversity Model and Growth Simulation of Tree

The living environment of trees is complex and changeable, resulting in different morphologies of trees. In order to depict the diversity and complexity of tree morphology, a simulation method of tree growth based on model decomposition was proposed. Firstly, we built diversified 3D tree models. The actual data of trees were measured, and used to fit tree trunk and crown shape curves based on the B spline function. Using the taper equation, the trend of trunk diameter was simulated. Meanwhile Direct3D API was used to realize the 3D tree morphology modeling. Secondly, the tree model was decomposed into 9 sub-models on the basic of the tree morphological characteristics. Finally, according to the topology relationship, sub-models were organized dynamically by linking scene nodes. Growth models of DBH, tree height, under branch height, crown height and crown width were used to calculate the tree morphological parameters by multithread parallel technology on multi-core processor, which represented the crown morphology in the cardinal directions at different age stages. And sub-models were controlled to realize the growth simulation of forest tree. The result shows that the method combines the 3D tree models with tree growth models closely. Meanwhile the under branch heights, crown heights, crown widths of trees in different directions grow accurately by growth models driving. The growth states in each direction of forest trees is simulated. The FPS of 3D rendering is always more than 25 and the average FPS is around 50 during trees growth. The direction heterogeneity of tree growth is simulated.