Interactive multiple anisotropic scattering in clouds

Abstract

We propose an algorithm for the real time realistic simulation of multiple anisotropic scattering of light in a volume. Contrary to previous real-time methods we account for all kinds of light paths through the medium and preserve their anisotropic behavior.Our approach consists of estimating the energy transport from the illuminated cloud surface to the rendered cloud pixel for each separate order of multiple scattering. We represent the distribution of light paths reaching a given viewed cloud pixel with the mean and standard deviation of their entry points on the lit surface, which we call the collector area. At rendering time for each pixel we determine the collector area on the lit cloud surface for different sets of scattering orders, then we infer the associated light transport. The fast computation of the collector area and light transport is possible thanks to a preliminary analysis of multiple scattering in planeparallel slabs and does not require slicing or marching through the volume.Rendering is done efficiently in a shader on the GPU, relying on a cloud surface mesh augmented with a Hypertexture to enrich the shape and silhouette. We demonstrate our model with the interactive rendering of detailed animated cumulus and cloudy sky at 2-10 frames per second.

An inverse problem approach for automatically adjusting the parameters for rendering clouds using photographs

“…Although our method can handle higher order scattering, increasing the scattering order results in greater amount of precomputed data. One solution would be to cluster high orders of scattering into several sets (e.g., 2, 3-4, 5-6, and so on) as proposed by Bouthors et al [2008]. Furthermore, we can compress the precomputed data using, e.g., wavelets.…”

“…This makes it time-consuming to adjust the parameters so that the desired appearance of clouds is produced. In order to address this problem, real-time rendering methods have been proposed [Harris and Lastra 2001;Bouthors et al 2008;Zhou et al 2008]. However, as we have mentioned previously, these methods only solve the forward problem.…”

3D Virtual worlds and the metaverse

“…Some of these techniques can see immediate applicability in virtual world environments, as they involve exterior environments, such as terrain, lighting, bodies of water, precipitation, forests, fields, and the atmosphere [Hu et al 2006;Wang et al 2006;Bouthors et al 2008;Boulanger et al 2009;Seng and Wang 2009;Elek and Kmoch 2010] or common objects, materials, or phenomena, such as clothing, reflected light, smoke, translucence, or gloss [Adabala et al 2003;Lewinski 2011;Sun and Mukherjee 2006;Ghosh 2007;Shah et al 2009]. Techniques for specialized applications, such as surgery simulation [Hao et al 2009] and radioactive threat training [Koepnick et al 2010], have a place as well, because virtual world environments strive to be as open-ended as possible with minimal restrictions on the types of activities that can be performed within them (just as in the real world).…”

Interactive albedo editing in path-traced volumetric materials

“…Our goal paths of length 2 paths of length 3 and more direct illumination indirect illumination single scattering multiple scattering is to extend this rich (but linear) theory to the non-linear problem of editing heterogeneous material albedos. Recently, a precomputation approach has been applied to volumetric materials by Bouthors et al [2008], but not with the purpose of editing the materials.…”