Volumetric shadow mapping
Pascal Gautron, Jean‐Eudes Marvie, Guillaume François · 2009
Figure 1: The light volume is sampled in shadow map space to compute single scattering, accounting for occlusions and shadows. The computation is carried out using graphics hardware for real-time performance (a, b, c), or RenderMan for production-quality rendering (d). Classical rendering methods usually consider that light travels in vacuum, hence overlooking its interactions with its medium of transmission: the air. However, interactions between light and par-ticles in suspension in the air generate phenomena such as smoke, fog, dust... Existing methods for simulating such interactions often rely on the native fog attenuation of graphics hardware, ignoring the occlusion effects shown in Figure 1. Mitchell [2005] tackles this problem by shading series of semi-transparent volume slices using a shadow map. While providing visually pleasant results, the method is not physically accurate and is prone to artifacts in given viewing directions due to undersampling. Our approach builds upon two unrelated rendering techniques: the well-known shadow mapping algorithm [Williams 1978] and sub-