code: func NewRay(o, v Vec) Ray {
  	//v = v.Normalize()
  	return Ray{
  		o:    o,
  		v:    v,
  		invv: Vec{1.0 / v.X, 1.0 / v.Y},
  	}
  }
docs: // NewRay creates a new Ray having the o as origin and v as direction of the
  // line.