Natural Environment Simulation-Research On Tree Modeling Method

Natural Environment Simulation is widely applied in the field of social production and life, especially in video studio, agricultural production, national defense and education. The tree modeling is one of the important research contents in natural environment simulation. Constructed realistic tree model is the key to expand the application of the tree model and therefore it has been widespread concerned in academia and industry. The scholars at home and abroad have completed a lot of researches on the modeling method; however these methods are limited to the self similarity algorithm or iterative algorithm. Therefore it can not describe consistent morphology of natural tree as well as it is difficult to represent the actual characteristics or motion in nature. The purpose of the research in this thesis is to solve how to construct realistic models of trees and reproduce natural state form swaying and broken trees in nature.The research significance and the present situation of tree modeling are analyzed and summarized firstly in this thesis. Then it proposes the new model and a set of effective modeling algorithm on many aspects aiming for the tree static model and dynamic model, such as, data structure, modeling algorithm, object force analysis and collision processing and so on. These methods can improve the system data storage capacity and response speed, strengthen the sense of reality, and accurately depict objects trajectory. Thus it can construct a real tree model in nature.Key techniques of tree modeling are concerned on the sample modeling, samples combined blanking, determining each fracture limit of the tree, analysis on force of wind and rain, determining the trajectory of fracture and swing range. Key problems cover the data structure, modeling algorithm, force analysis and collision processing. It includes the following aspects.(1) Four kinds of sample modeling are used to construct object modeling with expanding two and a half dimensional algorithm, which are simple standard sample, complex standard sample, simple deformed sample and complex deformed sample. As a result of half dimensional information includes change information of various samples, it stores characteristic information in database, for example, ends information and half dimensional information, making a small amount of data storage and a rapid lookup feature to quickly construct sample model.(2) Blanking algorithm will be used to construct the static model gradually with sample models. By "asperity" conversion, all samples are converted into convex body, and to judge whether two planes are parallel or intersecting by analyzing two related samples collision surface intersection. By the methods of sample-face-line transform, it gradually determines the intersection position and blanking parts between two "collisions", in order to be a combination of the two samples. Using this method can be constructed realistic model of a strong, realistic shape, and be able to demonstrate the true form of trees.(3) It constructs material model in the tree dynamic model. On the basis of static modeling, it considers rain and other natural phenomena in nature, and then fracture or swing. In order to describe the dynamic effect, it needs to calculate the fracture limit of tree each part. And then this value compared the power to determine fracture or swinging.(4) It constructs climate model in the tree dynamic model. After determination fracture limit value of each part, it is necessary to calculate the momentum of the external factors on the tree object. The wind and rain is the most common natural phenomenon in nature. In this thesis, it constructs wind model through wind speed and wind direction. Discussion of wind, rain force vertical or oblique acting on the tree object, using the momentum theorem to calculate momentum by establishing a link of speed, object volume and density characteristics, and then it determines the trajectory of force object.(5) The tree branches, leaves and other trees affected by external force, it will produce broken or swinging results. By coordinates, breaking objects in motion the thesis tries to determine the fracture occurring after being touched or oblique collision with other objects, solve the collision force and impacting the amount of time. These data determine fracturing object trajectory and collision object fracturing or swinging after collision. It constructs the tree kinematics model in the tree dynamic model.Research has been centred on key techniques, such as data structure, algorithm of object modeling, stress analysis and collision from the perspective of the tree modeling algorithm in this thesis. As a result, it provides efficient and complete tree modeling method, reproducing realistic tree form in nature.