Research On GPU-Based Direct Volume Rendering

Direct Volume Rendering is an important research content of Visualization in Scientific Computing, it has been widely applied in many scientific filed at present. Traditional Volume Rendering limited to its low rendering speed, poor interactive shortcomings, however, the demand for the realistic and interactive of visualization is growing fast to the application areas.Based on the systematic research of basic principle, classical rendering methods and some accelerate technology of Direct Volume Rendering, aimed at the limitation of Direct Volume Rendering, we have researched the volume rendering pipeline and pre-process accelerate technology, ray casting and hybrid volume rendering based on GPU. The contributions and relevant work in this paper are as follows:Firstly, an accelerated pre-process algorithm based on GPU is presented. We have analyzed the volume rendering pipeline based on GPU, to solve the bottleneck of the speed of pipeline, the new algorithm first partition the volume data adaptively and eliminate the empty region of sub-data, then convert the sub data to sub-textures, finally, it use the algorithm called VTP to packing the sub-textures to volume textures, which fits the texture memory of GPU. The results show that the proposed method improves the pipeline and accelerates the rendering speed.Secondly, a single pass ray casting of volume rendering based on GPU is presented. We have analyzed classical ray casting and texture mapping of volume rendering, to solve the problems of large memory requirement and time costing of pre-compute gradient, we map the ray casting based on CPU into GPU, compute the gradient use fragment shader on the fly. Compared to the traditional ones, the proposed single pass algorithm do the rendering in one pass without re-read data or re-write the color buffer, and the proposed algorithm can meet the requirements of the interactive rendering.Thirdly, a hybrid volume rendering based on GPU is proposed. Based on the research of the existed hybrid algorithms, to solve the complex of intersections between ray and hybrid data and poor rendering effects, we present a new first intersection algorithm between ray and isosurface. The results show that when rendering hybrid data, the speed of the proposed algorithm is faster than the old ones.Finally, we have developed a framework named GRV based on analyses and implementation of algorithms above. The results demonstrate that the framework develops GPU performance, reduces CPU overhead and improves the rendering frame rate significantly. It is a simple, fast and flexible framework for real-time and interactive of Direct Volume Rendering.