Abstract
We present a simple, fast solution for reflectance acquisition using
tools that fit into a pocket. Our method captures video of a flat target
surface from a fixed video camera lit by a hand-held, moving, linear
light source. After processing, we obtain an SVBRDF.
We introduce a BRDF chart, analogous to a color "checker" chart,
which arranges a set of known-BRDF reference tiles over a small
card. A sequence of light responses from the chart tiles as well as
from points on the target is captured and matched to reconstruct the
target's appearance.
We develop a new algorithm for BRDF reconstruction which works
directly on these LDR responses, without knowing the light or camera
position, or acquiring HDR lighting. It compensates for spatial
variation caused by the local (finite distance) camera and light position
by warping responses over time to align them to a specular
reference. After alignment, we find an optimal linear combination
of the Lambertian and purely specular reference responses to match
each target point's response. The same weights are then applied to
the corresponding (known) reference BRDFs to reconstruct the target
point's BRDF. We extend the basic algorithm to also recover
varying surface normals by adding two spherical caps for diffuse
and specular references to the BRDF chart.
We demonstrate convincing results obtained after less than 30 seconds
of data capture, using commercial mobile phone cameras in a
casual environment.