Sparse Ellipsometry: Portable Acquisition of Polarimetric SVBRDF and Shape with Unstructured Flash Photography

TL;DR

This paper introduces a portable, fast, and comprehensive method for capturing polarimetric SVBRDF and 3D shape using unstructured flash photography, significantly reducing acquisition time and device complexity.

Contribution

It presents a novel handheld device and inverse rendering algorithm for simultaneous polarimetric SVBRDF and shape acquisition, improving speed and portability over traditional ellipsometry.

Findings

Achieves accurate polarimetric BRDF measurements with 20-30 minute scans

Uses off-the-shelf optical components for portability

Demonstrates strong agreement with ground-truth datasets

Abstract

Ellipsometry techniques allow to measure polarization information of materials, requiring precise rotations of optical components with different configurations of lights and sensors. This results in cumbersome capture devices, carefully calibrated in lab conditions, and in very long acquisition times, usually in the order of a few days per object. Recent techniques allow to capture polarimetric spatially-varying reflectance information, but limited to a single view, or to cover all view directions, but limited to spherical objects made of a single homogeneous material. We present sparse ellipsometry, a portable polarimetric acquisition method that captures both polarimetric SVBRDF and 3D shape simultaneously. Our handheld device consists of off-the-shelf, fixed optical components. Instead of days, the total acquisition time varies between twenty and thirty minutes per object. We develop a complete polarimetric SVBRDF model that includes diffuse and specular components, as well as single scattering, and devise a novel polarimetric inverse rendering algorithm with data augmentation of specular reflection samples via generative modeling. Our results show a strong agreement with a recent ground-truth dataset of captured polarimetric BRDFs of real-world objects.