3D 형상 모델의 실시간 절단 기법과 응용에 대한 연구
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Manipulation of the 3D model data is an important research topic. The 3D based computation and reconstruction method such as polygon cutting technique can enhance the analysis or processing job of the modeling data to be much more perceptual one. The virtual cutting technique for 3D model is especially helpful in removing the overlapped parts of the model for easier observation. Since, the virtual cutting of 3D models can simulate the cutting process of real objects in detail the method can be employed to obtain the optimal operation scheme in advance for dangerous and safety critical working environment. If the method is applied in 3D games, it can enhance the sense of reality as the player can perceive the visual feedback of the game. For the sake of these purpose, the thesis investigates how to carry out virtual cutting for the 3D surface model in a practical way. Although the conventional cutting tool can carry out the virtual cutting task quickly, the cutting fragments can appear in an unwanted manner, since it adopts the infinite plane to conduct a holistic cutting of the model. Therefore, the thesis made corresponding modification to the original virtual cutting tool kit. And the modified version of the tool could conduct local cutting on the model and produce no fragments. The thesis contained a series of work on the following aspects. (1) Cutting Tool Two kinds of interactive cutting tools of the triangular plane and the 2D cutting segment are adopted in this thesis, and whose interactive method are also designed and realized. To use the triangular plane in virtual cutting, we should bind the plane, as a sub-object, with the cutting tool. When the cutting tool collided with the cut object, we could define an infinite cutting plane according to the three vertices of the triangular plane bound with the cutting tool. The cutting surface then divided the object. In the case of the 2D cutting segment, we used mouse to draw on the screen a segment with a starting point and an ending one. Based on this line and the observation direction of the Camera, we could define an infinite cutting plane, and conducted the virtual cutting. (2) Design and Realization of the Local Cutting Skills The thesis made certain modifications to the original Turbo Slicer Tool Kit, which adopted the infinite cutting surface in virtual cutting, to make it capable for local cutting on models. And the original virtual cutting tool, Tool Kit, produced fragments in dealing with complicatedly shaped models as it utilized the infinite plane to divide the model into two parts. Consequently, the thesis established a controllable cutting scope when virtual cutting was conducted on models, so that the virtual cutting was only conducted on the model's surface grid within the cutting scope. But the definition of the cutting scope varied due to the different cutting tools employed. (3) Grid Partitioning and the Realization of the Model Reconstructing Method The thesis utilized the plane equation of the cutting surface to determine whether the surface network of the object intersects with the cutting surface. If so, the intersection coordinated should be obtained, which were in turn changed into the matrix coordinates based on the standard transformation matrix algorithms proposed by Benjamin Zhu in 1992. The new grid vertices were inserted in the according positions to partition the grid. After that, the polygons composed of the newly added grid vertices were divided into triangles. We replicated the cut object after the partitioning, and reconstructed the grid structure of the two resulted models according to the connecting relationship of the vertices. Hence the reconstructing of the portioned models were completed. (4)Local Cutting Technology's Application: Reactor Disassembling Analog System The thesis realized the modification of local cutting based on the original virtual cutting. To test the practicability of the local virtual cutting, a reactor virtual disassembling system is established based on the structure of the 4th reactor set at the Fukushima Nuclear Power Station, utilizing the local virtual cutting technology proposed by this thesis, and achieved the expected results.