An exhaustive study of particular cases leading to robust and accurate motion estimation
For decades, there has been an intensive research effort in the Computer Vision community to deal with video sequences. In this paper, we present a new method for recovering a maximum of information on displacement and projection parameters in monocular video sequences without calibration. This work follows previous studies on particular cases of displacement, scene geometry, and camera analysis and focuses on the particular forms of homographic matrices. It is already known that the number of particular cases involved in a complete study precludes an exhaustive test. To lower the algorithmic complexity, some authors propose to decompose all possible cases in a hierarchical tree data structure but these works are still in development (T. Vieville and D. Lingrand, Internat. J Comput. Vision 31, 1999, 5-29). In this paper, we propose a new way to deal with the huge number of particular cases: (i) we use simple rules in order to eliminate some redundant cases and some physically impossible cases, and (ii) we divide the cases into subsets corresponding to particular forms determined by simple rules leading to a computationally efficient discrimination method. Finally, some experiments were performed on image sequences acquired either using a robotic system or manually in order to demonstrate that when several models are valid, the model with the fewer parameters gives the best estimation, regarding the free parameters of the problem. The experiments presented in this paper show that even if the selected case is an approximation of reality, the method is still robust. (C) 2002 Mevier Science (USA).
particular cases homographies perspective paraperspective and orthographic projections