Research On Techniques Of The Growth And Deformation Of Virtual Plant Organs

The study on visual techniques of the virtual plant is a main part of the researches of the virtual agriculture, which has potential applications ranging from simulation system of large nature landscape, education and virtual entertainment to digital agriculture. Therefore, the representation, modeling and rendering of plants has been one of the prevailing topics. Accordintg to the plant with the complicated structure and different form, its growth always contains many kinetics and biological rules. In contrast to the extensive studies on modeling plant architecture, the researches on dynamic modeling of plant organs still remain unexplored. Therefore, the study of image and biology based reconstruction of plants organs has a great practical value. Based on image process, the physical and biological principles this thesis aims to simulate the growth and deformation of plant organs driven by physiological mechanism. We seek to strike a balance between the realism of growth and the efficiency of caculating and rendering, to meet the requirement of dynamic displaying plant organs. The main study and contributions in this dissertation are given as followings:Firstly, it states the basic concepts of plant models and compares different methods of modeling virtual plants; then a multiscales analysis based approach to reconstruct 3D plant branching structure automatically for virtual plants is proposed. Initially, the Two Dimensional Hierarchical Automata (2DHA) responsible for plant branching structure development control was built. And then, the morphological and geometrical sampling data have been taken from several trees belong to the same species on the scale of growth unit (GU) and metamer, respectively.After that, we analyze GUs statistical properties and relations utilizing hidden markov tree model (HMT), for specific type of GU, the semi-markov chain model (SMC) is also employed to characterize metamer sequence. The result of multiscales analysis mentioned above acting as parameters of 2DHA to automatically control 3D reconstruction procedure. Finally, it puts out a way to product the L-system automacially by the sampling data from the plant. Therefore, the growth rules of the plant can be got from the ways based on the data statistics.Secondly, it provides a way to fit the curve of the plant organ's contour, which uses the Particle Swarm Optimization(PSO) based multi-object optimization to get the control parameters in the B spline .Therefore,the modified curve can get the result of approximating to source curve and smoothing effect. External repository and diversity solution are employed to prevent the PSO from converging too quickly. Moreover, the search policy of split-and-merge makes the selection of knots parameter more flexibly in B-spline bases computation while getting the discrete control points set of the target area and realizing the multi resolution interpolation.Thirdly, an algorithm of the leaf growth is proposed in this dissertation, which realizes the multiscale change of the physiological parameter by using the feedback control system. Initially, the plant branching structures are described by 2DHA, and the disturbance function completes the interaction between physiological parameter and botanic growth stimulant. And then, the growth stimulant not only changes the organic details but also influences the environment parameters, which modifies the plant branching structure in return. Then, the varying vein texture is synthesized by reaction-diffusion principle based on the canalization hypothesis. Finally, the three-dimension deformation of a leaf is implemented by bending the controllability grid. Experiment shows that this algorithm can effectively simulate the varying process of leaf texture and its form with the changing physiological parameter.Fourthly, after analyzing the process of the simulating the the plant growth by extended L-system deeply, it puts out a way to show the bloom progress which uses the Open L-system and the Bézier surfaces. And those surfaces represent the components of flower, for example petal, sepal and stamen or pistil. It constructs a variational model according to the biological principles.In the end, a plant fruit modeling method based on curve parametric equations is introduced. This approach addresses the issue of plant fruit modeling using fruit axis and sectional curve parametric equations to compute meshes and normal of vertexes in fruit surface. Then perturbation functions are added to curve parametric equations to solve the deformation of fruit growth. Finally, it builds a series of gradient model of the fruit by the 3D morphing, which makes up for a deficiency that deformation is motiveless in parametric equations.