Flexible Image-Based Photometric
Reconstruction using Virtual Light Sources
Simon Gibson, Toby Howard, and Roger Hubbold.
Computer Graphics Forum (Proceedings of Eurographics 2001),
19(3), Manchester, UK, September 2001 (to appear).
Abstract
Photometric reconstruction is the process of estimating the
illumination and surface reflectance properties of an environment,
given a geometric model of the scene and a set of photographs of its
surfaces. For mixed-reality applications, such data is required if
synthetic objects are to be correctly illuminated or if synthetic
light sources are to be used to re-light the scene. Current methods of
estimating such data are limited in the practical situations in which
they can be applied, due to the fact that the geometric and
radiometric models of the scene which are provided by the user must be
complete, and that the position (and in some cases, intensity) of the
light sources must also be specified {\it a-priori\/}. In this paper,
a novel algorithm is presented which overcomes these constraints, and
allows photometric data to be reconstructed in less restricted
situations. This is achieved through the use of {\it virtual
light sources\/} which mimic the effect of direct illumination from
unknown luminaires, and indirect illumination reflected off unknown
geometry. The intensity of these virtual light sources and the surface
material properties are estimated using an iterative algorithm which
attempts to match calculated radiance values to those observed in
photographs. Results are presented for both synthetic and real scenes
that show the quality of the reconstructed data and its use in
off-line mixed-reality applications.
Copyright The Eurographics Association and Blackwell
Publishers 2001. Published by Blackwell Publishers, 108 Cowley Road,
Oxford OX4 1JF, UK and 350 Main Street, Malden, MA 02148, USA.