invdlt

 function [xy] = invdlt(A,XYZ)
 Description:    This program calculates the local (camera) xy coordinates
        of a known point XYZ in space using the known DLT coefficients
        of that specific camera.
        This program can for instance be used to plot finite helical 
               axes into stereo x-rays. (similar procedure to Blankevoort 
        et al. (1990), J.Biomechanics 21, 705-720)
 Input:    - A:    11 DLT coefficients. A has to be 11x1 in size.
        - XYZ:  three dimensional coordinates of point in space
            XYZ can have several rows (different time/points)
            XYZ must have 3 columns: X,Y,Z
 Output:    - xy:    camera coordinates ([x,y])
            xy will have the same number of rows as XYZ
 Author:    Christoph Reinschmidt, HPL, The University of Calgary
 Date:        November, 1996
 Last changes: November 29, 1996
 Version:    1.0
 References:    e.g.: Nigg and Herzog (1995) Biomechanics of the musculo-
              skeletal system. Wiley and Son., p. 265.