A Study On Point-Based Global Illumination Effects

Realistic Graphics has always been one of the important branches of Graphics, and rendering is a key step of drawing realistic images. In rendering, because the global illumination effects can greatly simulate the light transmission between objects, it has been widely studied. Based on the performance of global illumination effects with traditional methods, this paper focuses on the point-based global illumination effects, improves a recent rendering technology--point-based rendering techniques, which include point-based ambient occlusion technology and point-based indirect lighting technology, which were finally used in practical systems.In the aspect of the ambient occlusion technology, firstly, this paper uses an open-source Tenderer "Pixie" to achieve the traditional ray tracing-based ambient occlusion, which is standard to evaluate the quality of effects of other methods. And then the ambient occlusion algorithm be divided into object space ambient occlusion and screen space ambient occlusion, and both of the two parts of content will be discussed and studied separately. In the part of object space, this paper implements the classic Bunnell algorithm and on this basis improves the algorithm, the result shows that the improved algorithm obtain high quality effects than the original, and has a certain robustness; In the part of screen space, with the realization of the traditional screen space ambient occlusion algorithm, this paper proposes and implements improved screen space ambient occlusion algorithm, and the result shows that the new algorithm accelerates speed. In addition, due to the general noise problems in screen space algorithm, this paper achieves and compares three noise reduction methods and obtains a comparative analysis.In the aspect of the indirect lighting technology, firstly, this paper uses "Pixie" to achieve the traditional photon mapping-based indirect lighting, which is standard to evaluate the quality of effects of other methods. Based on the realization of Bunnell’s indirect illumination algorithm, this paper describes and realizes Christensen Algorithm, and then describes Brick Map data structure which applies for the storage of point cloud and used in this algorithm. Finally this paper comes to a conclusion among the effects and speed in comparison.Finally, this paper introduce the furniture display system, highlighting one of the rendering technology, including real-time rendering and offline rendering, applies point-based rendering technology into offline rendering, and implements a room scene effects of ambient occlusion and indirect lighting, indicating that the technology’s potential and rendering application.