filename     : Meng15a.pdf
entry        : toappear
conference   : SIGGRAPH 2015, Los Angeles, USA, 9-13 August, 2015
pages        : 13
year         : 2015
month        : August
title        : Multi-Scale Modeling and Rendering of Granular Materials
subtitle     :
author       : Johannes Meng, Marios Papas, Ralf Habel, Carsten Dachsbacher, Steve Marschner, Markus Gross, Wojciech Jarosz
booktitle    : ACM Transactions on Graphics (TOG) - SIGGRAPH 2015 Conference Proceedings
ISSN/ISBN    :
editor       : 
publisher    : ACM
publ.place   : New York, NY, USA
volume       : 34
issue        : 4
language     : english
keywords     : physically based rendering, granular media
abstract     : We address the problem of modeling and rendering granular materials such as large structures made of sand, snow, or sugar where an aggregate object is composed of many randomly oriented, but discernible grains. These materials pose a particular challenge as the complex scattering properties of individual grains, and their packing arrangement, can have a dramatic effect on the large-scale appearance of the aggregate object. We propose a multi-scale modeling and rendering framework that adapts to the structure of scattered light at different scales. We rely on path tracing the individual grains only at the finest scale, and by decoupling individual grains from their arrangement we develop a modular approach for simulating longer-scale light transport. We model light interactions within and across grains as separate processes and leverage this decomposition to derive parameters for classical radiative transport, including standard volumetric path tracing and a diffusion method that can quickly summarize the large scale transport due to many grain interactions. We require only a one-time precomputation per exemplar grain, which we can then reuse for arbitrary aggregate shapes and a continuum of different packing rates and scales of grains. We demonstrate our method on scenes containing mixtures of tens of millions of individual, complex, specular grains that would be otherwise infeasible to render with standard techniques.