Research On Contact Deformation Of Soft Tissue And Collision Detection In Virtual Surgery Simulation

Virtual surgery is an important application of virtual reality technology in modern medicine and education.It has the advantages of repeatability,risk-free and low cost.It is the development trend of future surgical training and personalized precise treatment in the future.However,how to achieve real visual perception and real-time tactile feedback is still an urgent problem to be solved in virtual surgery research.In order to achieve real and fast visual haptic effects,this paper studies the three aspects of soft tissue deformation model,collision detection and deformation feedback.First,in order to achieve realistic visual effects,it is necessary to establish an accurate and realistic soft tissue deformation model.Therefore,a mass spring model based on vector springs is proposed in this paper.Vector spring calculates the spring force according to the angle between the initial vector and the real-time vector between two adjacent particles,thus achieving the ability of spring to resist bending and improving shape recovery ability of mass spring surface model.The experimental results of shape recovery ability test indicate that compared with the traditional mass spring model,the mass spring model based on vector spring has a more realistic deformation effect.Second,collision detection is the basis for deformation and feedback force calculation.The real-time,stability and accuracy of collision detection will have a tremendous impact on the accuracy of deformation simulations and the visual and tactile interactions of the entire virtual surgical system.In order to achieve rapid detection of collisions between surgical instruments and soft tissue models under the condition of ensuring accuracy,two new collision detection algorithms are proposed for soft tissue simulation systems.One is a discrete collision detection with volume structure which can extend the range of detection by body structure.This collision detection is applicable to high-precision,low-speed surgical scenarios;the other is hybrid collision detection with volume structure,which improves the disadvantages of discrete collision detection with volume structure by introducing the interpolation technology from the continuous collision detection algorithm,it is applied to highprecision and high-speed surgical scene.The results of the collision detection experiment show that the proposed new collision detection algorithm not only has the similar accuracy of traditional continuous collision detection,but also takes much less time.Finally,a deformation feedback algorithm based on positional constraint is proposed for the scene where the surgical instruments and the soft tissue are touched during surgery.This algorithm allows the model moves along with the surgical instruments to simulate the real touch effect.The real-time and touch feedback test results show that the proposed virtual surgery simulation system can realistically and accurately simulate surgical touch operations under the premise of meeting the realtime performance of the system.