Study On Visualization Technology Of Crop Morphology

Virtual crop is to simulate crop morphological architecture and growth progress in 3D space visually on computer, at the levels of organ, individual and population which are taken as the study objects. The visual crop is a deepening and expansion of crop growth simulation system, and has important realisti(?) meaning and wide application prospect in agronomic study and teaching, and crop growth design and management control. The primary objectives of this study were to adopt the multidisciplinary theories and technologies from crop science, computer graphics and virtual reality for studying wheat and rice growth, develop the key techniques for crop morphological modeling, realistic rendering, organ deformation simulation,3D reconstruction of crop canopy as well as collision detection and response on the basis of morphogenesis model, and then establish the crop growth visualization system based on model integration and component design. The anticipated results would lay a technical foundation for further constructing the model-based digital crop system.Firstly, the methods of parameterized geometry modeling were applied to crop organ morphological modeling. Based on observation and analysis on morphological structure of rice and wheat organs, an architectural parameter-based geometrical model for crop organ formation was developed by using 3D geometric modeling technology. The model included 5 submodels:leaf blade geometry, leaf sheath geometry, stem geometry, wheat spike geometry and rice panicle geometry submodels. The NURBS were used to simulate leaf blade and sheath, and stem geometry submodel was developed by a cylinder. Wheat spike geometry submodel was developed by means of assembling single organ:spike axis was simulated with a cylinder, spikelet was simulated with an ellipsoid and a cylinder. Bezier curves were used to simulate dynamics of the panicle axis curve, and panicle axis was simulated by mapping panicle axis curve to 3D. Primary and secondary branches were simulated with a part of panicle axis and a cylinder, and spikelet was simulated by an ellipsoid and a cylinder. Based on topographic structure of rice panicle, the rice panicle geometrical model was developed. The main parameters of model were the length and width of leaf, the angle of leaf, the length of leaf sheath, the length and diameter of stem, the length of panicle, the panicle-neck angle, and so on. The model could describe the dynamic growth processes of 3D morphological structure of organs, and all the parameters had definite biological meanings. Additionally, the model can be easily integrated wtih crop morphogenesis model, and thus lay a foundation for realization of crop visual growth.Based on organ geometry model, realistic crop organs were realized on the computer by combining with texture mapping, color rendering and illumination treatment. To deform crop organs, the method of object deforming driven by skeleton was applied to crop organ. Curling and twisting deformation of leaf was explored, and then a skeleton driven method for deforming leaf was proposed. Firstly, the leaf skeleton was generated. It consisted of a venation skeleton and some detailed skeletons generated from the venation skeleton. Secondly, the leaf skeleton was deformed, and the leaf mesh was mapped to the deformed leaf skeleton, as such the deformation of the leaf mesh followed the deformation of the leaf skeleton. Finally, the proposed techniques were applied to simulate wheat leaf deformation including curling and twisting. The results on leaves deformation demonstrated that the proposed approach is applicable for simulating deformation of cereal leaves with realistic effects.Since the conventional method for plant growth modeling is difficult to be applied to crop visualization, a method for visualizing individual plant growth progress was proposed, which combining organ visual model with morphogenesis model by using a tree structure. Firstly, with the growth pattern of individual plant, a crop tree was developed by using the output parameters of crop morphogenesis model, for describing crop growth information (including organ geometric information and plant topology characteristics). Secondly, to obtain some information about crop growth, the crop tree was traversed in level-order based on time sequence of crop growth. Finally, the visualization of individual plant growth was realized based on organ visual model. The implemented results showed that the visual method could correctly describe the geometric and topologic characteristics of individual plant, and realize the dynamic growth processes of 3D morphology of crop plant. This method could serve as key technology for visualizing crop population growth.With the technologies of mesh simplification and Level-of-Detail, a method for simulating crop population growth was proposed. Firstly, on the basis of crop population morphogenesis and differences among the single plants, individual plant model with different levels of detail was constructed, combining with the mesh simplification technology and the method of View-Dependent Level-of-Detail. Secondly, an algorithm for visualizing crop population at multiple levels of detail was proposed. The algorithm used different detail models, partitioned the space and chose different detail according to the view related factors. Finally, real-time rendering of crop population was realized on the basis of visualization of individual plant growth. The experiment results showed that the method for visualizing crop population could correctly describe the characteristic architecture of crop population, which would lead to the development of visual crop growth system.Adopting the collision detection and response methodology into the field of crop growth visualization, an algorithm used for collision detection between leaves defined by NURBS surfaces was developed based on the techniques of surface subdivision and hybrid hierarchical bounding volume (HHBV). Firstly, the leaf surface was subdivided by using the technique of inserting node. Additionally, a HHBV tree for the subdivided leaf based on AABB and FDH was developed. The HHBV tree used AABB as its root node for fast overlap test, and used FDH as other nodes for accurately determining the contact status between leaves in closer proximity. Secondly, an algorithm for collision detection based on the HHBV tree was proposed. Finally, based on leaf morphological architecture, reasonable and efficient solutions for collision response were presented to satisfy different collisions between leaves. Further results proved that the algorithm was efficient for realizing population growth simulation, and helpful for improving the precision and reliability of a visual crop.Finally, driven by weather, soil, variety and management databases and integrating crop morphogenesis model and growth visualization model, a model-based crop growth visualization system was established using component-based software technology. The system was programmed with Visual C++.net, the OpenGL library and Access database. The implemented system could be used for predicting growth progress and visualizing morphological architecture of wheat and rice plants under various growing environments and management strategies. The visualization system for crop 3D morphology on organ, individual and population levels should be useful for improving the level of digitalization of crop growth system and further developing virtual farming technology.