Physically based lighting model for cloth and its validation

We present a new approach to modeling lighting in cloth based on a confirmed assumption that cloth yarns are scattering media. The paper proposes a way to calculate Bi-directional Reflectance Distribution Function (BRDF) of a yarn by integrating the yarn's Bidirectional Sub-Surface Scattering Reflectance Distribution Function (BSSRDF) over the yarn's surface. The yarn’s BSSRDF is obtained via a Monte-Carlo ray tracing simulation of scattering and absorption of light within yarn's volume. We demonstrate that the new approach is physically plausible by showing the correspondence of scattering patterns of the incident light between our modeled cloth sample and a piece of a real cotton cloth. The scattering pattern of a real cloth is acquired via direct measurement performed with a proprietary measurement apparatus.