code: @Pure
  	public static Point3f computeLineLineIntersection(
  			double x1, double y1, double z1, double x2, double y2, double z2,
  			double x3, double y3, double z3, double x4, double y4, double z4) {
  		double s = computeLineLineIntersectionFactor(x1, y1, z1, x2, y2, z2, x3, y3, z3, x4, y4, z4);
  		if (Double.isNaN(s)) {
  			return null;
  		}
  		return new Point3f(
  				x1 + s * (x2 - x1),
  				y1 + s * (y2 - y1),
  				z1 + s * (z2 - z1));
  	}
docs: Replies the intersection point between two lines.
  <p>
  Let line equations for L1 and L2:<br>
  <code>L1: P1 + factor1 * (P2-P1)</code><br>
  <code>L2: P3 + factor2 * (P4-P3)</code><br>
  If lines are intersecting, then<br>
  <code>P1 + factor1 * (P2-P1) = P3 + factor2 * (P4-P3)</code>
  
  @param x1 is the first point of the first line.
  @param y1 is the first point of the first line.
  @param z1 is the first point of the first line.
  @param x2 is the second point of the first line.
  @param y2 is the second point of the first line.
  @param z2 is the second point of the first line.
  @param x3 is the first point of the second line.
  @param y3 is the first point of the second line.
  @param z3 is the first point of the second line.
  @param x4 is the second point of the second line.
  @param y4 is the second point of the second line.
  @param z4 is the second point of the second line.
  @return the intersection point or <code>null</code> if no intersection.