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Structure and motion

In the previous section it was seen how different views could be related to each other. In this section the relation between the views and the correspondences between the features will be used to retrieve the structure of the scene and the motion of the camera. This problem is called Structure and Motion.

The approach that is proposed here extends [7,67] by being fully projective and therefore not dependent on the quasi-euclidean initialization. This was achieved by carrying out all measurements in the images. This approach provides an alternative for the triplet-based approach proposed in [36]. An image-based measure that is able to obtain a qualitative distance between viewpoints is also proposed to support initialization and determination of close views (independently of the actual projective frame).

At first two images are selected and an initial reconstruction frame is set-up. Then the pose of the camera for the other views is determined in this frame and each time the initial reconstruction is refined and extended. In this way the pose estimation of views that have no common features with the reference views also becomes possible. Typically, a view is only matched with its predecessor in the sequence. In most cases this works fine, but in some cases (e.g. when the camera moves back and forth) it can be interesting to also relate a new view to a number of additional views. Once the structure and motion has been determined for the whole sequence, the results can be refined through a projective bundle adjustment. Then the ambiguity will be restricted to metric through self-calibration. Finally, a metric bundle adjustment is carried out to obtain an optimal estimation of the structure and motion.



Subsections
next up previous contents
Next: Initial structure and motion Up: Visual 3D Modeling from Previous: Three and four view   Contents
Marc Pollefeys 2002-11-22