Real Time Single Scattering Effects

Rendering mist, haze or fog remains a challenge in current computer graphics since it is intrinsically a 3D problem. While the attenuation caused by fog is easy to implement, single scattering effects such as glows and shafts of light, that increase considerably the realism, are harder to render in realtime. This paper addresses the rendering of such effects along with volumetric shadows induced by shadow casters in the participating media. Whereas techniques related to shadow maps have been explored when rendering with single scattering, this paper proposes a real-time algorithm using the philosophy of shadow volumes, including volumetric shadows. With a spatial coherence method, simple shaders and an intensive use of the stencil buffer, we render the shadow planes in a back to front order to obtain the correct volumetric shadows. Therefore our method is easy to integrate in a graphics engine using the shadow volume technique since it requires only a little additional texture memory and is implemented with simple shaders. Realistic images can be produced in real-time for usual graphic scenes and at a high level framerate for complex scenes, allowing changes in the properties of participating medium, animations of objects and even light sources movements. Keywords— Single scattering, Real Time, Hardware rendering