docs: static void computeRotation(DMatrix3 t , DMatrix3x3 R ) {
  		for (int i = 1; i >= 0; i--) {
  			double a = t.get(i,0);
  			double b = t.get(i+1,0);
  
  			// compute the rotator such that [a,b] = [||X||,0]
  			double r = Math.sqrt(a*a + b*b);
  			double q11 = a/r;
  			double q21 = b/r;
  
  			// apply rotator to t and R
  			t.set(i,0,r);
  			t.set(i+1,0,0);
  
  			if( i == 1 ) {
  				R.a11 = 1; R.a12 =  0;   R.a13 =  0;
  				R.a21 = 0; R.a22 =  q11; R.a23 = q21;
  				R.a31 = 0; R.a32 = -q21; R.a33 = q11;
  			} else {
  				R.a11 = q11;  R.a12 = R.a22*q21; R.a13 = R.a23*q21;
  				R.a21 = -q21; R.a22 = R.a22*q11; R.a23 = R.a23*q11;
  			}
  		}
  	}