Illuminating and Rendering Heterogeneous Participating Media in Real Time using Opacity Propagation

We present a new approach to illuminate and render single scattering effects in heterogeneous participating media in real time. The medium’s density is modeled as a sum of radial basis functions, and is then sampled into a first volumetric grid. We then integrate the extinction function from each light source to each cell in the volume by a fast cell-to-cell propagation process on the GPU, and store the result in a second volume. We finally render both scattering medium and surfaces using a regular step ray-marching from the observer to the nearest surface. As we traverse the medium, we fetch data from both volumes and approximate a solution to the scattering equation. Our method is real-time, easy to implement and to integrate in a larger pipeline. Figure 1: Left : the original scene. Right : a scattering media is added.