Fogshop: Real-time design and rendering of inhomogeneous, single-scattering media

Figure 1: Rendering of scattering media. A point light source is located at the gargoyle’s mouth. Notice the shadowing and haloing effects in (d). We describe a new, analytic approximation to the airlight integral from scattering media whose density is modeled as a sum of Gaus-sians. The approximation supports real-time rendering of inhomo-geneous media including their shadowing and scattering effects. For each Gaussian, this approximation samples the scattering in-tegrand at the projection of its center along the view ray but models attenuation and shadowing with respect to the other Gaussians by integrating density along the fixed path from light source to 3D cen-ter to view point. Our approach handles isotropic, single-scattering media illuminated by point light sources or low-frequency environ-mental lighting. We also generalize models for reflectance of sur-faces from constant-density to inhomogeneous media, using sim-ple optical depth averaging in the direction of the light source or all around the receiver point. Our real-time rendering approach is incorporated into a system for real-time design and preview of re-alistic, animated fog, steam, or smoke