Combining Generative and Discriminative Models in a Framework for Articulated Pose Estimation |
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Authors: | RÓMer Rosales Stan Sclaroff |
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Affiliation: | (1) Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA;(2) Image and Video Computing Group, Dept. of Computer Science, Boston University, Boston, MA 02215, USA |
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Abstract: | We develop a method for the estimation of articulated pose, such as that of the human body or the human hand, from a single
(monocular) image. Pose estimation is formulated as a statistical inference problem, where the goal is to find a posterior
probability distribution over poses as well as a maximum a posteriori (MAP) estimate. The method combines two modeling approaches,
one discriminative and the other generative. The discriminative model consists of a set of mapping functions that are constructed
automatically from a labeled training set of body poses and their respective image features. The discriminative formulation
allows for modeling ambiguous, one-to-many mappings (through the use of multi-modal distributions) that may yield multiple
valid articulated pose hypotheses from a single image. The generative model is defined in terms of a computer graphics rendering
of poses. While the generative model offers an accurate way to relate observed (image features) and hidden (body pose) random
variables, it is difficult to use it directly in pose estimation, since inference is computationally intractable. In contrast,
inference with the discriminative model is tractable, but considerably less accurate for the problem of interest. A combined
discriminative/generative formulation is derived that leverages the complimentary strengths of both models in a principled
framework for articulated pose inference. Two efficient MAP pose estimation algorithms are derived from this formulation;
the first is deterministic and the second non-deterministic. Performance of the framework is quantitatively evaluated in estimating
articulated pose of both the human hand and human body.
Most of this work was done while the first author was with Boston University. |
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Keywords: | human body pose hand pose nonrigid and articulated pose estimation statistical inference generative and discriminative models mixture models expectation maximization algorithm |
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