Rendering Discrete Participating Media with Geometrical Optics Approximation

TL;DR

This paper introduces a geometrical optics approximation-based Monte Carlo rendering framework for simulating light scattering in discrete participating media, capturing graininess and converging to continuous media with increased particle concentration.

Contribution

It presents a novel, efficient method combining GOA and Monte Carlo techniques to simulate discrete media with varying graininess levels, surpassing previous approaches.

Findings

Successfully simulates diverse discrete media appearances.

Converges to continuous media as particle concentration increases.

Provides a practical alternative to Lorenz-Mie theory for rendering.

Abstract

We consider the scattering of light in participating media composed of sparsely and randomly distributed discrete particles. The particle size is expected to range from the scale of the wavelength to the scale several orders of magnitude greater than the wavelength, and the appearance shows distinct graininess as opposed to the smooth appearance of continuous media. One fundamental issue in physically-based synthesizing this appearance is to determine necessary optical properties in every local region. Since these optical properties vary spatially, we resort to geometrical optics approximation (GOA), a highly efficient alternative to rigorous Lorenz-Mie theory, to quantitatively represent the scattering of a single particle. This enables us to quickly compute bulk optical properties according to any particle size distribution. Then, we propose a practical Monte Carlo rendering solution to solve the transfer of energy in discrete participating media. Results show that for the first time our proposed framework can simulate a wide range of discrete participating media with different levels of graininess and converges to continuous media as the particle concentration increases.