code: func (r Rectangle) Sub(v Vec3) Rectangle {
  	return Rectangle{
  		Vec3{r.Min[0] - v[0], r.Min[1] - v[1], r.Min[2] - v[2]},
  		Vec3{r.Max[0] - v[0], r.Max[1] - v[1], r.Max[2] - v[2]},
  	}
  }
docs: // Sub returns the rectangle r translated by -v.