Research On Tetrahedron Cutting And Optimization Methods In Virtual Surgery Simulation

Medicine is becoming one of the major application fields for Virtual Reality (VR), due to rapid development of Scientific Visualization in recent years. Virtual Surgery Simulation System is a medical Virtual Reality system dedicated to simulating the dynamic process in surgery. It involves visualization of medical data (usually anatomical), interaction with the visualized data, simulating behaviors of object deformation and feedback in modalities of vision, sound, force, touch, and smell. Virtual Surgery Simulation is a challenging research area, involving multiple fields such as Computer Graphics, Computer Vision, Biomechanics, Robotics and Medicine.Simulating cutting process of soft tissue and organs is a very important part of Virtual Surgery Simulation. Tetrahedron is widely used to construct the geometric model of virtual organs. Efficient methods must be developed to split or merge tetrahedrons in order to adapt to topology changes during cutting process. The topology changes also affect the stability of the deformation calculations of the model. Thus the main parts of this thesis are the two chapters on "Reconstruction of Tetrahedrons" and "Stability of Tetrahedrons".Main research works in this thesis are: 1) Reconstruction of Tetrahedrons.The cutting process changes the topology of the tetrahedron mesh. The topology changes are implemented by inquiring and updating data structures of neighboring tetrahedron elements. The inquiring and updating algorithms must be fast and efficient in order to meet the real time requirement of virtual surgery simulation. In this thesis a data structure based on simplex is introduced which can not only meet the above real time requirement, but also benefit the optimization process. Crack-free subdivision and minimal element subdivision methods are used for tetrahedron cutting.