A novel ray-shooting method to render night urban scenes a method based on polar diagrams

Illumination and shadows are essential to obtain realistic virtual environments. Nevertheless, large scenes like urban cities demand a huge amount of geometry that must somehow be structured or reduced in order to be manageable. In this paper we propose a novel real-time method to determine the shadowed and illuminated areas in large scenes, specially suitable for urban environments. Our approach uses the polar diagram as a tessellation plane, and a ray-casting process to obtain the visible areas. This solution derives the exact illuminated area with a high performance. Moreover, our approach is also used to determine the visible portion of the scene from a pedestrian viewpoint. As a result, we only have to render the visible part of the scene, which is considerably lower than the global scene.