The Deformation Model Of Soft Tissue Based On The Sphere-Filled Model For Virtual Surgery System

In recent years, Virtual Reality technology has come into the public view.Because of its authenticity, immersion, interactivity, autonomy, etc., Virtual Reality is widely used in entertainment, medicine, education, military, aerospace and other fields. In the field of modern medicine, Virtual Surgery is an important application of Virtual Reality, it can save the cost of training young doctors, increase the success rate of surgery, provide development environment for the developers of medical equipment, etc. So currently, the study of the technology for virtual surgery system is a very hot field. After analyzing the advantages and disadvantages of several frequently-used deformation models, such as Free Form Deformation Model,Chain-Mail Model, Mass-Spring Model, Finite Element Model and Mass Tensor Model, the paper studies and implements an improved Mass-Spring Model, that is Sphere Filled Model.Firstly, the data of the model should be got before modeling. After process the result of Tetgen's output, the data expected can be got. The sphere of the Sphere-Filled model is the particle with physical property such as mass and rotational inertia, and the spheres are linked by springs with the material property of elongation,flexion and torsion. Then this paper introduces the concepts of collision model,behavioral model and visualization model, and also implements a mapping algorithm and a collision detection algorithm based on Bounding Sphere.Then the deformation process is analysed. Because the springs have the material property of elongation, flexion and torsion, three corresponding mechanics equation sets are calculated, and springs would exert forces and torques upon spheres. Then,combine these forces and torques with external forces(such as interaction force and gravity), spheres' force condition are clear. So spheres' equation sets of motion can be solved. Furthermore, this paper introduces the algorithm of updating the vertex positions by using the mapping relations.At last, this paper describes the system framework, device module and rendering module and show the experimental results. The conclusions got from the results are:the deformation model of soft tissue based on the Sphere Filled Model could satisfy the demand of real-time, the effect of deformation is good and has very strong universality.