Research Of GPGPU-based Real-time High-quality Ray Casting

To meet the requirements of medical imaging visualization and3D visualization arts,with the evolution of CPU\GPU, researches about volume rendering are focused onachieving real-time high-quality effects on consumer PC hardware. In the directions ofreal-time multi-resolution rendering of mass volume data, advanced illumination modelsand transfer function setting and effective classification, progress has been made, but muchwork needs to be done.In this thesis, I focused mainly on the solutions to the problems of how to achievereal-time volume rendering and improve the qualities of rendering results to meet thedemands of medical application. Therefore, I have chosen GPU to speed up ray casting inparallel, and analysed reasons for artifacts and then proposed an effective anti-artifactalgorithm, and worked on illumination models to strengthen photorealistic of the resultimages.In summary, I have made some innovation in the following aspects:1） With GPU evolving into GPGPU, NVIDIA brought out CUDA, and researchesabout accelerating volume rendering with GPU have turned to GPGPU-basedmethods, from texture slicing and shader-based methods. In this thesis, I haveconsidered details of implementing ray casting and achieved more than1000timesof speedup ratio with CUDA, so solved the problem of how to achieve real-timevolume rendering.2） In this thesis, I have considered artifacts produced in all stages of volumerendering, analysed deeply the reasons for wood-grain artifact, discussed threeimplementation methods of pre-integration which have physical meanings, andproposed an effective anti-artifact algorithm which merges stochastic jittering andpre-integration together. Meanwhile, I have done research about details ofimplementing single scattering, and used it to highlight volume structure. It hasbeen proved that high-quality rendering can be got with the algorithm proposed inthis thesis, at the same time the problem about rendering time can be handled verywell.3） I have implemented isosurface rendering with ray casting, and done research aboutadvanced illumination models. An algorithm of real-time high-quality isosurfacerendering, which merges Blinn-Phong local lighting, shadow, ambient occlusionand subsurface scattering together, has been proposed. 4） I have designed a software system of3D visualization, which supports reading andwriting medical images, interactive setting of1D transfer function and simplevolume clipping. It has good meanings for engineering application.Therefore, I have solved effectively the problem about rendering time and imagequality. The work stated in this thesis has good meanings for medical practice or3Dvisualization arts.