Research Of Real-Time Global Illumination Model In Complex Scenes

With the extensive application of virtual reality technology, people increasingly demands for the realism of the virtual scene. Global illumination is one of the key technologies to render realistic scenes, lighting effects to simulate a variety of physical make the whole scene look more realistic. Due to the global illumination calculation is too large, it is difficult to realize real-time rendering in interactive graphics applications. Especially a large number of facets for complex scenes, as well as the complex positional relationship between the various facets, it is prominent that contradiction between photorealistic rendering and real-time rendering. In this paper, in view of realistic rendering for complex scenes, introduces several illumination model, and carries on the experiment in virtual golf game scene, which meet real-time rendering and get improvement for render effects.Firstly, the research for basic principle of screen space ambient occlusion. By using the frame buffer as approximate discrete values of scene geometry, the shadow separates out from the complexity of the scene. By2D scene data in screen space simulated3d information, it calculates projection coordinate for each pixel sampling point in the depth buffer. Through the projection point of AO approximately takes the place of the sample point AO, and Gaussian blur method to reduce noise of rendering results, it verifies the efficiency and results for algorithm by OpenSceneGraph.Secondly, the research for real-time illumination model based HDR. In view of the physical light model in real life, it achieves real-time rendering of HDR lighting model in virtual scene. The original virtual scene as input, resampling its virtual scene to extract the average brightness, filtered bright areas and the establishment of a halo effect, high dynamic range image is mapped to the low dynamic range image output to the normal display by tone mapping operator.Finally, Due to progressive photon mapping algorithm is large computation, it is great challenge to achieve real-time. This paper presents a cross-platform algorithm of progressive photon mapping parallelization based on OpenCL. In this algorithm, by improving serial mode and optimizing parallelism in progressive photon mapping, combined with OpenCL programming architecture, different parts of workload are settled in suitable processors to take full advantage of multi-core CPU and many-core GPU parallel computing capabilities. Eye ray tracing, photon tracing and scene rendering, are performed on GPU, which are scheduled by CPU. Experimental results show that efficiency of progressive photon mapping can be greatly improved by OpenCL-based Parallel algorithm. It verifies photorealistic renderings of the above illumination models on the platform of virtual golf game system, that can satisfy the real-time rendering efficiency.