Research On Indoor Real-time Global Illumination Technology

Global illumination takes into account light both coming directly form light sources(direct illumination) and reflecting off all surfaces in the scene(indirect illumination). The images created using global illumination are more photorealistic and natural-looking than images lit with direct light only. Global illumination looks great, but traditional techniques for calculating it are far too slow for real-time applications. Render times for global illuminated scenes are often measured in hours per frame. Render times for a frame in real-time applications are measured in milliseconds, thus, most applications only account for direct illumination and an constant ambient light component, and much research has focused on rendering scenes with complex geometry and materials, less has been done on rendering scenes with large numbers of light sources. Generally, rendering cost increases linearly with the number of lights. The complexity of the global illumination especially many-light global illumination has been limiting its use to off-line applications.In this paper, the current global illumination algorithms is analyzed, and light map combined with instant radiosity is used to render the indoor scene which is closed,many lights and objects including light can be moved freely. Indirect illumination of the single brighter light is computed on GPU, while the direct illuminations of other lights are pre-computed and stored as lightmaps, thus all the object indoor can be moved freely, and dynamic objects can not only receive indirect illumination from other parts of the scene but also can generate indirect illumination effects. The direct illumination of other lights are pre-computed and stored as lightmaps, combining the contribution of dynamic lights and the resulting indirect illumination from it with lightmaps makes the rendering global illumination of the many-lights scene with dynamic representative light and dynamic camera achieves interactive rates.The main work is as follows:1,We find the representative light by approximating many lights by a single brighter light. Paraboloid mapping is used for the shadow maps of this representative light for the purpose of uniform sampling to the whole indoor scene. Former instant radiosity computed on GPU mainly rely on the traditional shadow mapping for the generation of RSMs, which is restricted by view frustum, and can only be used for lights with a limited field of view but impossible for lights with a greater field of view. Later cube mapping is used to generate shadow map for 180 degree and full 360 degree field of view, but the scene is rendered six times from the position of point light which makes it hard to achieve the interactive rates. Paraboloid shadow mapping used in this paper both sample the greater field of view and achieve interactive rates.2,The direct illumination of other lights are pre-computed and stored as lightmaps on CPU. In order to achieve interactive rates all the shadows generate from lights except the representative light is ignored to avoid the time consuming occlusion test, the update of light map can be finished in milliseconds.3,Images are synthesized by computer through combining the indirect illumination computed on GPU and the direct illumination computed by CPU according to Phong lighting model, implementing the rendering global illumination of the many-lights scene with dynamic representative light and dynamic camera achieves interactive rates.