Their Technology Transfer Office has details of a “

__tripod operator” technology__of interest to those working with vision guided robotics (VGR) and meshing of 3D point clouds. The movie below provides an overview.

Despite viewing the movie a couple of times, I’m still not sure just what a “tripod operator” actually does. It looks almost as though it compares the relative heights of three nearby points and tries to infer something about the geometry.

The write-up says the NRL has a patent on this technology, but I’ve been unable to find it. If anyone out there has more luck perhaps you’d be kind enough to share.

## 2 comments:

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA293983

from the above - "The tripod operator is a class of feature extraction operators for range images which

facilitate the recognition and localization of objects. It consists of three points in 3-space

fixed at the vertices of an equilateral triangle and a procedure for making several scalar

measurements in the coordinate frame of the triangle. The triangle is then moved as a

rigid body until the three vertices lie on the surface of some range image or modeled

object. The resulting measurements are local shape features which are invariant under

rigid motions. These features can be used to automatically find distinctive regions at

which to begin recognition, to rapidly screen candidate objects for a match, and to speed

pruning in the generation of interpretation trees. Tripod operators are applicable to all

3-D shapes, and reduce the need for specialized feature detectors. A key property is that they can be moved on the surface of an object in only three DOF (like a surveyor's tripod

on the ground)."

see here

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA293983

"The tripod operator is a class of feature extraction operators for range images which

facilitate the recognition and localization of objects. It consists of three points in 3-space

fixed at the vertices of an equilateral triangle and a procedure for making several scalar

measurements in the coordinate frame of the triangle. The triangle is then moved as a

rigid body until the three vertices lie on the surface of some range image or modeled

object. The resulting measurements are local shape features which are invariant under

rigid motions. These features can be used to automatically find distinctive regions at

which to begin recognition, to rapidly screen candidate objects for a match, and to speed

pruning in the generation of interpretation trees. Tripod operators are applicable to all

3-D shapes, and reduce the need for specialized feature detectors. A key property is that

they can be moved on the surface of an object in only three DOF (like a surveyor's tripod

on the ground). Consequently, only a 3-dimensional manifold of feature space points can

be generated, for any dimensionality of feature vector. Thus, objects can be represented

compactly, and in a form allowing fast matching."

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