Work done at Inria Lorraine (Nancy, France).
Implementation of an algorithm for computing external visual hulls.

Summary

The understanding of a 3-dimensional scene with 2-dimensional pictures is a main challenge in computational vision. Consider an object in space, and an observer moving in a certain area which looks at the outlines of the object, that is, the image of the object projected on a screen.

It may well happen, in some cases, that the observer cannot reconstruct exactly the object with the informations that he can get. The "visual hull" of the object is the best approximation of this object when the observer moves into this area.

We present an algorithm (based on an article by S. Petitjean) for computing visual hulls for a scene in 2D when the observation area encloses completely the object and is, in some sense, "far" from it. This algorithm has been implemented in C++ language using the LEDA library.

Details

This worked has been done at Inria Lorraine, from 11 september to 11 december 1999, under the direction of Sylvain Lazard and Sylvain Petitjean. The final C++ code is around 1300 lines long (37 ko).

The report [French] is available (ps.gz, pdf, bib)

Reference: Sylvain Petitjean, A computational geometric approach to visual hulls, International Journal on Computational Geometry and Applications, 8(4):407-436, 1998.

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