Research On Realistic Rendering Methods Of Blood Based On Physics In Virtual Surgery

As one of the research hotspots of digital health, the virtual surgery system will offer doctors a lot of low-cost surgery trainings, give them chances to grasp this kind of surgery and improves the success rates of surgery. The realistic rendering of blood is one of the key technologies in virtual surgery system, and is accompanied with every cut doctors make. The effect of the realistic rendering of blood will not only directly influence the sense of reality of the virtual surgery system, but also train doctors to improve the ability of handle the bleeding cases. In order to realize the realistic rendering of blood, firstly we do some research on the simulation of soft tissue knifing, which can be used as the basis of the initialization of bleeding and the interface of this paper system and the modules of other members in our group; then, we perform numerical calculation for the blood simulation; finally, we achieve surface rendering for the blood to get the simulating result. This paper’s works mainly include:(1) In order to simulate the phenomenon of knifing soft tissues, we improve the vertex split algorithm and use it to the simulation of knifing soft tissues. In our improved algorithm, we use two arcs to simulate the edges of the incision and increase the number of discrete points of the incisions to make the shape of the incision to be more smoothly and get a more real effect.(2) Study on the nature of hemorheology, aiming at the problems that the dynamic models used in existing realistic rendering methods are with low accuracy, we introduce a kind of model with higher accuracy-Casson model into realistic rendering of blood, in order to make the rendering result to conform further to real physical rules.(3) In the processing of numerical calculation of blood, aiming at the problems that the item of viscous forces in discretization is complex when Smoothed Particle Hydrodynamics (called as SPH for short) method is used in Casson models, we present a processing scheme to simplify the item of viscous forces, using the average of the viscosity in last frame and making the Casson models to be discretized. On the other hand, we use nearest neighbor searching algorithm instead of traditional global searching algorithm to narrow the searching scope of SPH method working at the particle inside the enclosing scope, decrease the quantity of calculation and improve real-timing of the system.(4) In order to decrease the quantity of calculation in the modules of the surface rendering of blood, we present a pre-processing method to regulate the distribution of the particles to translate the irregular particles into regular the lattice of the cube’s corner points. Aiming at the problems that the number of the empty voxels in Marching Cubes algorithm is so large that the efficiency of the algorithm is low, we present an algorithm to segment the regions according to the density of the lattice of vertexes and use different algorithms to achieve surface rendering in different regions to increase the efficiency of the algorithm and the sense of reality.Finally, we designed and developed a bleeding simulation system according to the methods described above. In this system, we provide the functions of knifing soft tissues and the simulation of bleeding, good interactivity and strong sense of reality. The experimental results show that the blood simulated with the realistic rendering methods based on physics is with high sense of reality and good real-timing, our research has important implications for the research of improving the sense of reality in virtual surgery, with a wide range of application prospects.