| Surgical simulation is in great need for surgical training, analysis, planning and rehearsal. One of the core problems in this application is the real time deformation of the models for human organs. The deformable models must provide both realistic visual effects (graphics) and high fidelity force feedback (haptics) in real time, without distractive visual artifacts or misleading tactile clues. In view of the requirement of physical accuracy, physically based deformable models are desirable for surgical simulation.; Physically based deformable modeling has been a serious research topic for about twenty years in the computer graphics community. For computer animation, a great deal of work has been done so that the model can barely provide realistic (physically plausible) visual effects in real time. Surgical simulation has a much higher requirement for the deformable model. First, to meet the haptics update rate of 1000 Hz rather than the graphics update rate of 30 Hz, the cycle time for regenerating the deformable model decreases by a factor of 33. Second, the physical accuracy needed for high fidelity force feedback is much more challenging to achieve than realistic visual effects, for it results in much heavier computation.; Although there have been a lot of claims of successful application of physically based deformable models for computer animation, those models are far from mature for the applications supporting haptics, such as surgical simulation and emerging computer games supporting force feedback. The existing models are neither fast enough for real-time applications, nor can they provide both realistic deformations for graphics display and force feedback for haptics rendering. In view of this situation, it is essential to improve current deformable models or present better ones in terms of speed and physical accuracy when we aim to build a high fidelity surgical simulator for effective surgical training.; The scope of this dissertation is threefold. First, a new deformable model is proposed based on the structure and constitutive elements of human organs, which has potential to be more physically accurate though it can hardly meet the real time requirement for the current computer resources. Second, since the mass-spring-damper (MSD) model is currently the only deformable model able to meet the real time requirement, the physical accuracy of the 1D, 2D and 3D MSD models for both structured meshes and unstructured meshes is investigated based on continuum mechanics and the parameter optimization schemes are proposed and validated. Finally, the inguinal hernia surgery simulator is introduced and further research to apply the parameter optimization scheme is suggested. |
