Hemorheological Simulation And Its Application In Virtual Dental Surgery

Utilize a virtual surgical simulation system for preoperative drills,condition analysis,and evaluation of postoperative errors.Although the functional modules of existing virtual dental surgery systems are becoming increasingly sophisticated,due to their poor physical model stability and real-time performance,as well as unrealistic visual rendering,they are unable to quickly and stably simulate the process of blood injection,surging,and suction.Aiming at building a simulation of blood rheology with physical reality,real-time and visual reality,this paper proposes a high viscosity hemorheological model with dynamic pressure correction and adaptive boundary.The neighborhood search algorithm based on sequential grid,compact hash and Z sort quickly and realistically realizes the fluid mechanics characteristics of blood,and applies the hemorheological model and neighborhood search algorithm to the virtual dental surgery simulation system,A fast and realistic simulation of blood gushing and spraying after tooth extraction was presented.The research content of the paper is as follows:Firstly,in response to the problem of poor stability of physical models in traditional SPH models,a high viscosity hemorheological model with dynamic pressure correction and adaptive boundary is proposed.The model optimizes the hemorheological model from three aspects: dynamic pressure correction,viscous force stability,and boundary conditions.In response to the problem of excessive correction steady-state error in the pressure term in traditional SPH models,A dynamic pressure correction algorithm based on dynamic correction coefficients has been proposed.Compared with traditional SPH models in pressure correction,the steady-state error of the average density curve after 300 frames has been reduced from 22% to 6%,greatly reducing density oscillation and volume attenuation,making the total volume of blood stable during movement and the density of each position almost the same after blood stabilization;In response to the instability problem of high viscosity simulation,an implicit viscous force method was introduced to ensure the stability of high viscosity blood particles when μ > 0.75,achieving stable changes in blood particle velocity,and making the layered state and sense of hierarchy clearer during blood flow;An improved fluid solid coupling model is proposed for the boundary conditions of complex and deformable models,which eliminates the F-norm of the strain rate tensor at the boundary,ensuring the adhesion effect of blood flowing along the oral wall and the stability of blood morphology when dripping,and preventing rapid diffusion due to impulse action.Secondly,in response to the problem of poor real-time performance in traditional SPH models,this paper proposes a neighborhood search algorithm based on ordered grids,compact hashing,and Z-sorting.The neighborhood search algorithm provides fast solutions for the hemorheological model and improves the smoothness of virtual surgery operations.Compared to the neighborhood search algorithm in traditional SPH models,it solves the problem of multi threaded write competition and improves the construction and search efficiency of data structures.This algorithm reduces the computational time by 51.8% compared to traditional neighborhood search algorithms when searching 16000 blood particles in a simulated space with a width of 350(mm),greatly improving the real-time performance of blood rheology simulation.Thirdly,to solve the problem that the visual rendering of blood is not realistic,Bilateral filter algorithm is selected to smooth the curvature of the surface of blood particles,and then Lambert,Blinn Phong and Fresnel lighting models are mixed to render the blood particles,generating ambient light,diffuse reflection and specular highlight on the surface of blood particles,and completing the light rendering of the surface,so as to make the visual performance of the blood model more realistic.Finally,the aforementioned hemorheological model,neighborhood search algorithm,and rendering algorithm were applied to the virtual dental surgery simulation system,achieving a fast and stable virtual tooth extraction operation with real physical characteristics,and presenting a realistic visual effect of the hemorheological model.