class to construct a line with parametric form
Line = p + aV (a point and a direction vector on the line)
ported from C++ code by Song Ho Ahn (song.ahn@gmail.com)
class for a 3D plane with normal vector (a,b,c) and a point (x0,y0,z0)
ax + by + cz + d = 0, where d = -(ax0 + by0 + cz0)
ported from C++ code by Song Ho Ahn (song.ahn@gmail.com)