  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.
