Light structure from pin motion: Geometric point light source calibration
We
present a method for geometric point light source calibration. Unlike prior
works that use Lambertian spheres, mirror spheres, or mirror planes, we use a
calibration target consisting of a plane and small shadow casters at unknown
positions above the plane. We show that shadow observations from a moving
calibration target under a fixed light follow the principles of pinhole
camera geometry and epipolar geometry, allowing joint recovery of the light
position and 3D shadow caster positions, equivalent to how conventional
structure from motion jointly recovers camera parameters and 3D feature
positions from observed 2D features. Moreover, we devised a unified light
model that works with nearby point lights as well as distant light in one
common framework. Our evaluation shows that our method yields light estimates
that are stable and more accurate than existing techniques while having a
much simpler setup and requiring less manual labor. |