| Computer graphics combined with virtual reality(VR)technology to assist surgical simulation training is a hot research direction nowadays.The sense of reality in virtual surgery training has a great relationship with training efficiency and a better real experience can effectively shorten the learning cycle of novice doctors.The purpose of graphic rendering is to maximize the simulation of real world scenes.Physics-based rendering(PBR)is a technique to simulate the scattering,absorption and energy transfer of light in nature,which can better restore the visual color of the real world.In this paper,the application of bidirectional reflection distribution function(BRDF)and virtual reality in surgery is studied.It mainly includes the following aspects: 1.Studied and analyzed Lambert,Phong,Blinn-Phong and other common lighting algorithms.All above algorithms were verified on Unity 3D for different application scenarios.The differences of rendering effects in different application scenarios and the defects of the three algorithm models in physical rendering were summarized.2.Studied the physics-based rendering algorithm.Based on the Microfacet theory and combined with the diffuse reflection calculation processing in the Cook-Torrance algorithm and Disney algorithm,an improved Cook-Torrance model suitable for the real rendering of organic biological tissue was proposed in this paper and developed a custom BRDF shader based Unity 3D engine.Application test results show that compared with the traditional biological tissue rendering,the BRDF shader has a significant improvement in rendering realism,but the simulation of subsurface scattering was not obvious.3.Using above improved Cook-Torrance model and the self-developed BRDF shader in virtual surgery training simulation system,and verifying the shader’s real rendering effect in the system under the conditions of head-mounted display device and headless display device.The results show that BRDF shader outper forms the traditional rendering method in the sense of reality whether there is head-mounted display device or not.When head-mounted display device was available,the immersion of virtual surgery training is better than that of head-mounted display device.However,because head-mounted display device could generate vertigo,the user experience was not as good as that of head-mounted display device.4.Based on the good performance of BRDF shader in real rendering,we developed an Android application combining AR/VR CT 3d visualization,and named it iCTVie. |
