Simulation Research Of Virtual Surgical Cutting Scene Based On Meshless Model

The virtual surgery simulation system is of great research value as it can provide clinical surgery training for junior doctors and preoperative surgery rehearsal for pathology.To address the problem of black hollow areas on the surface of the kidney model,the paper proposes a repair method based on point cloud density,which makes the model more complete.Later on,for the problem of blurred and overlapping texture mapping when the traditional spherical crown mapping method is applied to the surface of irregular models,a region-based spherical crown mapping algorithm is proposed to improve the texture effect of the model surface.To address the problem of narrow-shaped incisions in traditional cutting methods,the paper uses third-order Bessel curves to fit surgical incisions for different cutting situations,and adopts SPH method and Open GL hybrid method for rendering inside the incisions,and finally establishes a virtual surgical simulation system to present more realistic cutting wounds during cutting operation simulation.The following research work has been accomplished in this paper.Firstly,the three-dimensional model of kidney organ is established in Mimics software with Computed Tomography medical image data,and the point cloud addition algorithm is designed to fill the black cavity for the problem of black cavity on the surface of kidney model.The algorithm uses the point cloud density to determine the black cavity location,and adopts the bilinear interpolation method to add the point cloud to the black cavity area,which makes the model more consistent with the real soft tissue in appearance effect.For the blurring and overlapping of texture mapping when dealing with models with large surface curvature changes,the paper proposes a region-based spherical crown mapping algorithm,which divides the model into flat and non-flat regions according to the surface curvature of the model,and then performs texture mapping for different regions according to the algorithm designed in this paper,which effectively solves the blurring and overlapping of texture mapping in the traditional spherical crown mapping algorithm.Second,this paper conducts a simulation study for cutting operations in virtual surgical systems.In order to better judge whether to start the cutting operation on the model,and to improve the accuracy of force feedback and more comprehensively describe the biomechanical properties of soft tissue,a spring damping model based on point cloud density is proposed to better simulate the feedback force on the scalpel.When the simulation system starts cutting,this paper divides the soft tissue cutting into two cases according to the real soft tissue cutting process: the simulation of soft tissue surface cutting and soft tissue internal cutting.For the two different cutting cases,the scalpel simplification models are different.The starting point is determined by detecting the cutting path of the interactive device and calculating the point cloud where the displacement occurs,and the control point is determined by using the designed algorithm in the point cloud where the displacement occurs,and the third-order Bessel curve is determined by the control point and the starting point to draw the shape of the cutting wound.The model is textured and the cut wound is rendered according to the new point cloud position after displacement.Finally,it is experimentally verified that using third-order Bessel curves to perform cutting operations on the meshless kidney model improves the realism of the cutting surgery simulation system.Then,the interior of the cut wound is rendered based on a hybrid rendering method of SPH and Open GL.A blood model based on the smooth particle fluid dynamics(SPH)algorithm was first constructed to determine the neighboring points of the particles by the particle’s domain of action,and then the force,acceleration and SPH particle expressions were calculated based on Newton’s law.After finishing building the dynamics of the particles,rendering of smooth and flat fluid is also required to realize real blood.In this paper,we use the blending function of Open GL to set the transparency of blood surface particles,which not only realizes the rendering of blood,but also improves the fidelity of the virtual surgery system to a certain extent.Finally,the virtual surgical simulation platform was built,and the black cavity-filled kidney model and texture mapping algorithm and the surgical cutting method and the rendering method of the wound interior were applied to the system.The experimental results show that the virtual surgery simulation system developed in this project can effectively complete the surgical cutting operation with realistic visual effects.