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Semi dynamic light maps

Öztürk, Bekir
One of the biggest challenges of real-time graphics applications is to maintain high frame rates while producing realistically lit results. Many realistic lighting effects such as indirect illumination, ambient occlusion, soft shadows, and caustics are either too complex to render in real-time with today's hardware or cause significant hits to frame rates. Light mapping technique offers to precompute the lighting of the scene to speed up expensive lighting calculations at run-time. This allows rendering high quality lights from a high number of light sources even on low-end devices. The primary drawback of this technique is that scene state that is dependent on the precomputed data cannot be changed at run-time. This includes intensity, color, and position of light sources as well as position and visibility state of light map illuminated objects. This property of light maps significantly decreases the interactability of applications. In this thesis, we present a method to remove some of these restrictions at the cost of additional texture memory and small CPU/GPU workload. This allows changing color and intensity properties of selected light sources at run-time while keeping the benefits of light mapping technique. It is also becomes possible to change visibility state of selected objects. Our algorithm computes the light maps separately for each light source. Regions shadowed by each selected object are also captured and stored. These maps are later combined at run-time to correctly illuminate the scene. Despite the increase in the generation time of precomputed data, the overhead of the method at run-time is low enough to make it useful in many real-time applications.