/** Compute the distance from a point pta
* to the line defined by the 2 points ptb and ptc
* The two points ptb and ptc defining the baseline also define
* its positive direction from point ptb toward point ptc.
* It is assumed that the 3 points pta, ptb, ptc define a plane
* not far from the X-Y plane.
* The sign of d is positive if the point pta
* is left of the line ptb=>ptc
* The sign of d is negative if pta is right of the line.
*
* @author Robert Laine alias Sailcuter
*/
real Distance3d(const CPoint3d &pta, const CPoint3d &ptb, const CPoint3d &ptc)
{
real d;
CVector3d Va = CVector3d( pta - ptb );
CVector3d Vb = CVector3d( ptc - ptb).normalized();
CVector3d Vd = CVector3d::crossProduct(Vb, Va);
d = Vd.length();
if ( Vd.z() < 0 )
d = -d;
//
return d;
}
