code: public Point3i getCellIndices(Tuple3d pt) {
  		Point3d p = new Point3d(pt);
  		this.transfToCrystal(p);
  
  		int x = (int)Math.floor(p.x);
  		int y = (int)Math.floor(p.y);
  		int z = (int)Math.floor(p.z);
  		return new Point3i(x,y,z);
  	}
docs: Get the index of a unit cell to which the query point belongs.
  
  <p>For instance, all points in the unit cell at the origin will return (0,0,0);
  Points in the unit cell one unit further along the `a` axis will return (1,0,0),
  etc.
  @param pt Input point (in orthonormal coordinates)
  @return A new point with the three indices of the cell containing pt