  This paper is concerned with recovery of motion and structure parameters from
multiframes under orthogonal projection when only points are traced. The main
question is how many points and/or how many frames are necessary for the task.
It is demonstrated that 3 frames and 3 points are the absolute minimum.
Closed-form solution is presented. Furthermore, it is shown that the task may
be linearized if either four points or four frames are available. It is
demonstrated that no increase in the number of points may lead to recovery of
structure and motion parameters from two frames only. It is shown that instead
the increase in the number of points may support the task of tracing the points
from frame to frame.
