Research On VCT Global Illumination Algorithm For Large-scale Scene In Virtual Reality

It is one of the most important problems in virtual reality that restoring real illumination information in virtual scene,and it is also an important source of virtual environment's reality and immersion.At present,many scholars use the global illumination algorithm to render the virtual scene.However,the global illumination not only simulates the direct illumination in the scene,but also simulates the indirect illumination,such as reflection,refraction,caustic and so on.This results in a high computational cost,especially in large-scale scenarios,where the model data is large,the computation of global illumination is heavy,and the process is complicated.Therefore,a high quality and high performance global illumination algorithm is the primary goal of researchers.In this paper,the global illumination algorithm is studied.By analyzing and comparing the advantages and disadvantages of different algorithms,a global illumination algorithm based on voxel cone tracing technology is designed and implemented.This algorithm can guarantee the efficient operation in large scale scenes.Firstly,in voxelization stage,a new type of scene illumination information representation structure “cascade voxel texture” structure is proposed in this paper.According to this structure,the voxelization algorithm is improved.The structure saves the storage space of the scene greatly by representing the scene hierarchically.At the same time,the information on each side of the voxel is stored so this structure has anisotropy.Compared with the original algorithm,the efficiency of improved voxelization algorithm is improved significantly.Secondly,at the stage of illumination calculation,this paper proposes an improved cone tracing filter based on the cascaded voxel texture structure.The improved filter has an excellent performance in filtering efficiency.The voxel cone tracing algorithm is optimized to improve the efficiency of light injection and reflected light calculation based on the improved cone tracing.To further improve the run-time frame rate of the algorithm,the voxel updating strategy is improved in this paper.Finally,this algorithm can handle the optical radiation generated by two reflections in a dynamic,large-scale,and complex scene under interactive performance.It also achieves excellent results when simulating diffuse reflections,specular reflections,ambient light and other light shading effects.