X1,X2,X3,X4分别为4个点的三维坐标，例如X1=[1,2,3]，本程序可以计算出直线X1X2与X3X4的交点P的坐标X，如果直线X1X2与X3X4不相交，则给出的是直线X1X2与X3X4的公垂线在直线X1X2上的垂足的坐标。-X1, X2, X3, X4 are 4 three-dimensional coordinates of points, such as X1 = [1,2,3], the program can calculate the intersection of line P X1X2 and X3X4 coordinates X, X1X2 and X3X4 if the line does not intersect , is given a straight vertical public X1X2 and X3X4 X1X2 on the pedal in a straight line coordinates.