Research On Real-time Global Illumination Algorithm For Low Performance Platforms

As one of the hottest research directions in computer graphics,global illumination technology plays a crucial role in enhancing the realism of virtual scenes.However,due to the high computational cost,current global illumination algorithms basically rely on devices with high-performance GPUs to render virtual scenes in real time.In recent years,virtual reality technology has been applied in various fields,among which the virtual simulation experiment of architectural light environment design has become an important teaching tool for architecture,urban and rural planning and other majors by virtue of the experiential experimental process and intuitive teaching demonstration.In order to facilitate the use of students and experimental teaching,the virtual simulation experiment system is usually released as a Web project.However,the memory and computing resources that the browser can apply are much smaller than those of the client running on the PC,and the mainstream 3D engines on the market currently do not support rendering global illumination in real time on the Web platform.And the realism of the virtual scene determines the teaching quality of the virtual simulation experiment system,while the application of light is also a very important part of the experimental teaching.Therefore,it is necessary to design an algorithm that supports real-time rendering of global illumination in low-performance platformsIn this thesis,the real-time global illumination algorithm for low-performance platforms is the object of study,and the main work is:(1)In this thesis,we propose a visibility clustering algorithm based on virtual point light for reducing the computational resources consumed by the visibility computation between light sources and scene points.The visibility calculation between two points is one of the main computational costs in the global illumination algorithm,and a reasonable simplification and approximation of the visibility calculation is the key to bringing the algorithm up to real-time rendering rates.In this thesis,we use virtual point light to approximate the calculation of indirect illumination and cluster the visibility information between virtual point light and scene points based on the similarity between adjacent virtual point light sources and the similarity between adjacent scene points.The experimental results prove that the algorithm in this thesis has a fast rendering rate in complex scenes with a large number of facets and can render global lighting effects with a good sense of realism.(2)In this thesis,we propose a KD-Tree based light forest construction algorithm for reducing the rendering consumption of multi-light scenes where there are large-scale light source collections.In the global illumination algorithm based on the idea of light cut,the clustering process of the light source collections in the scene is to organize the light source collections into a light tree.The construction time of the light tree grows as the number of light sources rises,so the construction time of the light tree becomes a bottleneck in the performance of the algorithm in multi-light scenes with large sets of light sources.In this thesis,we use KD-Tree to divide the light source collection into several light source clusters according to the distribution characteristics of the light sources in the scene,and build the light tree on each light source cluster.The experimental results demonstrate that the algorithm in this thesis is more efficient and scalable compared with other light source clustering algorithms in a multi-source scene with a large-scale light source collection,and can render global illumination in real time on low-performance platforms.(3)A prototype system for virtual simulation experiments of architectural light environment design based on the real-time global illumination algorithm proposed in this thesis is designed,and the performance of the system is evaluated through experiments.