A line represented by a point and a direction. Several methods work with a
parameter that can be used to specify a point on the line. For instance
Line3d l = new Line3d( new Point3d(0,0,0), new Vector3d(2,0,0) );
System.out.println( l.getPoint( 0.0 ) );
System.out.println( l.getPoint( 1.0 ) );
will print the points (0,0,0) and (2,0,0). Similarly, the lines
l.orthogonalProjection(new Point3d(1,1,0));
l.orthogonalProjectionParameter(new Point3d(1,1,0));
will return the point (1,0,0) and the parameter 0.5 respectively.