| The analysis of tree disturbance under wind load mainly involves two aspects: the structure of 3D model of trees and the movement state of trees under different wind speed.The research on 3D model of trees has been developed for several decades,and has achieved good results through the joint exploration of the staff in various fields.However,because of the particularity of the tree structure,the existing model of tree 3D model has a poor sense of reality.The biggest challenge to realize the dynamic simulation of trees under the wind load is the complexity of the structure of trees,tree have many variety,Morphological diversity,both branch and leaves will motion under wind force,The simulation of tree motion includes the motion of branches and leaves,Therefore,the motion morphological change of the tree under wind force has been a hot and difficult point in the research field.Based on the above background,this thesis combines the material mechanics and the aerodynamic knowledge to realize the simulation of the tree movement,And a lot of experiments are carried out to analyze the disturbance of trees under the action of wind force.The main research work is as follows:(1)3D model construction of trees: In this thesis,use skeleton extraction method,the point cloud data is scanned by laser point cloud scanner,Division point cloud data into several segment,extracting tree skeleton to build 3D tree model,get the branch node position information.Skeleton extraction method is mainly based on Dijkstra distance algorithm,calculated Minimum distance between data point,As the basis of data clustering,a class of data is referred to as a skeleton,the linear programming method is used to calculate the proportion of distance and angle,the nodes of each type of data are connected based on weighted matching degree,Set the appropriate radius value on skeleton,and finally get the complete tree skeleton model.(2)Wind field simulation:the wind in nature change constantly,in order to make the wind field simulation more close to natural wind,the variability of wind is constructed by using Perlin noise function,On the basis of the existing wind field increased the variability of wind to realize the natural wind simulation.(3)Force analysis of trees: The complex structure of the tree has many branches and leaves,Therefore,it’s unrealistic to analysis force on whole tree,in this thesis,through the analysis of single tree branches and leaves,to calculated the position of the coordinate points and falling state of each branch a leaves after deformation under wind force,Finally,the motion under wind force of tree is obtained by the whole synthesis.(4)On the basis of 3D model of trees,Wind field model,theoretical analysis of the under wind force movement,Using VC++ development environment,combined with OpenGL texture mapping technology,double buffering technology and stack technology to achieve the visual simulation of the movement of trees under the wind field.(5)Through visual simulation system,adjust different wind parameters and tree attribute parameters to realized tree disturbance analysis under wind force. |
