Robust structure from motion using motion parallax

An efficient and geometrically intuitive algorithm for reliably interpreting the image velocities of moving objects in 3-D is presented. It is well known that under a weak perspective the image motion of points on a plane can be characterized by an affine transformation. It is shown that the relative image motion of a nearby non-coplanar point and its projection on the plane is equivalent to motion parallax, and because it is independent of view rotations it is a reliable geometric cue to 3-D shape and viewer/object motion. The authors summarize why structure from motion algorithms are often very sensitive to errors in the measured image velocities and then show how to efficiently and reliably extract an incomplete qualitative solution. They also show how to augment this into a complete solution if additional constraints or views are available. A real-time example is presented in which the 3-D visual interpretation of hand gestures or a hand-held object is used as part of a man-machine interface. This is an alternative to the Polhemus coil instrumented Dataglove commonly used in sensing manual gestures