double precision function kutl_distance_line_line(point1, eta1,
     *                                                  point2, eta2)
*
* begin_doc
*
*  Returns distance between two lines
*
*  Input Parameters:
*  point1(3)      double precision array
*                 (x,y,z) of initial point defining line 1
*
*  eta1(3)        double precision array
*                 direction cosines of line 1 (do not have to be normalized)
*
*  point2(3)      double precision array
*                 (x,y,z) of initial point defining line 2
*
*  eta2(3)        double precision array
*                 direction cosines of line 2 (do not have to be normalized)
*
*  Output Parameters:
*
*  Other routines:
*
*  Notes:
*
*  >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
*  The lines are defined by
*                  x = x1 + eta1*r1
*                  x = x2 + eta2*r2
*
*    where r1, r2 are free parameters and eta1 and eta2 do not have to
*    be normalized to 1. The distance is calculated from
*
*                       delta*(eta1 x eta2)
*                d  =  ---------------------
*                          |eta1 x eta2|
*
*               where delta(i) = x2(i) - x1(i)
*
*    The sign convention is chosen to match what you would get for the
*    distance in the xy plane between a line and a point.
*
*  >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
*
*  Author:   Paul R Avery      Created:  Sun Nov 16 18:33:24 EST 1997
*
*  Major revisions:
*
*
* end_doc