 
Summary: Projective Visual Hulls
Svetlana Lazebnik1
(slazebni@uiuc.edu)
Yasutaka Furukawa1
(yfurukaw@uiuc.edu)
Jean Ponce1,2
(jponce@uiuc.edu)
1 Department of Computer Science and Beckman Institute
University Of Illinois, Urbana, IL 61801, USA
2 D´epartement d'Informatique
Ecole Normale Sup´erieure, Paris, France
Abstract. This article presents a novel method for computing the visual hull of a solid
bounded by a smooth surface and observed by a finite set of cameras. The visual hull
is the intersection of the visual cones formed by backprojecting the silhouettes found
in the corresponding images. We characterize its surface as a generalized polyhedron
whose faces are visual cone patches; edges are intersection curves between two viewing
cones; and vertices are frontier points where the intersection of two cones is singular, or
intersection points where triples of cones meet. We use the mathematical framework
of oriented projective differential geometry to develop an imagebased algorithm for
computing the visual hull. This algorithm works in a weakly calibrated settingthat
