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Photometric Reconstruction (2000-2001)
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 work, a novel algorithm has been developed
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. Below, we show results for real
scenes that show the quality of the reconstructed data and its use in
off-line mixed-reality applications.
S. Gibson, T.L.J. Howard, R.J. Hubbold, "Image-Based Photometric
Reconstruction for Mixed Reality", SIGGRAPH 2001 Sketches
and Applications Program, Los Angeles CA, USA, August 2001.
S. Gibson, T.L.J. Howard, R.J. Hubbold,
"Flexible Image-Based Photometric Reconstruction using Virtual Light
Sources", Computer Graphics Forum (Proceedings
of Eurographics 2001) 19(3), Manchester, UK, September 2001
(to appear).