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**Object Exploration By Purposive, Dynamic Viewpoint Adjustment**

K. N. Kutulakos, C. R. Dyer, V. J. Lumelsky,
Computer Sciences Department Technical Report 1124, University of Wisconsin - Madison, November 1992.

### Abstract

We present a viewing strategy for exploring the surface of an unknown object (i.e., making all of its points visible) by purposefully controlling the motion of an active observer. It is based on a simple relation between (1) the instantaneous direction of motion of the observer, (2) the visibility of points projecting to the occluding contour, and (3) the surface normal at those points: If the dot product of the surface normal at such points and the observer's velocity is positive, the visibility of the points is guaranteed under an infinitesimal viewpoint change. We show that this leads to an object exploration strategy in which the observer *purposefully* controls its motion based on the occluding contour in order to impose structure on the set of surface points explored, make its representation simple and qualitative, and provably solve the exploration problem for smooth generic surfaces of arbitrary shape. Unlike previous approaches where exploration is cast as a discrete process (i.e., asking where to look next?) and where the successful exploration of arbitrary objects is not guaranteed, our approach demonstrates that dynamic viewpoint control through directed observer motion leads to a qualitative exploration strategy that is provably-correct, depends only on the dynamic appearance of the occluding contour, and does not require the recovery of detailed three-dimensional shape descriptions from every position of the observer.