Method normalize

code/geometry/primitives3d.cpp:35–37

    point3d N = (B-A)*(C-A); double D = A%N;
    return ((*this)%N - D)/N.length(); }
  point3d normalize(double k = 1) const {
    // length() must not return 0
    return (*this) * (k / length()); }
  point3d getProjection(P(A), P(B)) const {
    point3d v = B - A;
    return A + v.normalize((v % (*this - A)) / v.length()); }