code: @SuppressWarnings("unused")
  	private static Atom calc_H(Atom C, Atom N, Atom CA)
  			throws StructureException {
  
  		Atom nc  = Calc.subtract(N,C);
  		Atom nca = Calc.subtract(N,CA);
  
  		Atom u_nc  = Calc.unitVector(nc)   ;
  		Atom u_nca = Calc.unitVector(nca);
  
  		Atom added = Calc.add(u_nc,u_nca);
  
  		Atom U = Calc.unitVector(added);
  
  		// according to Creighton distance N-H is 1.03 +/- 0.02A
  		Atom H = Calc.add(N,U);
  
  		H.setName("H");
  		// this atom does not have a pdbserial number ...
  		return H;
  
  	}
docs: Use unit vectors NC and NCalpha Add them. Calc unit vector and
  substract it from N.
  C coordinates are from amino acid i-1
  N, CA atoms from amino acid i
  
  @link http://openbioinformatics.blogspot.com/
  2009/08/how-to-calculate-h-atoms-for-nitrogens.html