Scene appearance from the point of view of a light source
is called a reciprocal or dual view. Since there exists a large
diversity in illumination, these virtual views may be non-
perspective and multi-viewpoint in nature. In this paper,
we demonstrate the use of occluding masks to recover these
dual views, which we term shadow cameras. We first show
how to render a single reciprocal scene view by swapping
the camera and light source positions. We extend this tech-
nique for multiple views by building a virtual shadow cam-
era array with static masks and a moving source. We also
capture non-perspective views such as orthographic, cross-
slit and a pushbroom variant, while introducing novel ap-
plications such as converting between camera projections
and removing refractive and catadioptric distortions. Fi-
nally, since a shadow camera is artificial, we can manip-
ulate any of its intrinsic parameters, such as camera skew,
to create perspective distortions.
Sanjeev J. Koppal and Srinivasa G. Narasimhan