AI coordinated motion – drift offset

I'm reading Ian Milligton's book on AI in the game

On page 150 he introduces the drift offset.

I do not understand how it works:


1) Imagine I have a formation with 2 possible positions (relative to the anchor): (-1, -1) and (1, -1)

2) The drift offset calculated from this information is (0, -1)

3) My anchor starts at position (1,0), has no speed and is in the center of mass of my formation

4) So if I follow the algorithm, my slots are (-1,1) and (1,1).

5) My anchor will stay at (1.0) as this is the center of gravity of the formation

6) I add a new slot (0, -2)

7) Follow the algorithm, drift offset is (0, -2). New slot position: (-1,2) – (1,2) and (0,0)

8) The anchor point is at (0.4 / 3), so it moves

Result


As you saw, when I was doing the algorithm, when I understood my anchor drift, do you know what I'm doing wrong?

Many Thanks

Combinatorics – Formula for the product of sums of pairwise co-ordinated dividers of $ n $.

Can we develop a formula for?

$$
r (n) = prod_ {
begin {array} {c}
x, y mid n \
(x, y) = 1
end {array}}
(x + y)
$$

In words, this is the product of the sums of all coprime pairs of divisors of $ n $,

For example
$$ r (12) = (1 + 2) (1 + 3) (1 + 4) (1 + 6) (1 + 12) (2 + 3) (3 + 4) = 191100 $$

There is some information on the number of coprime divisor pairs (A063647).