Function backward

backward(chain: Chain2, base: readonly [number, number]): Chain2
The backward pass: pins the base and pushes each bone outward from it. The basebone constraint is applied here.
Parameters
- chain: Chain2
  the chain to move, mutated in place
- base: readonly [number, number]
  where the base should go, used only when chain.fixedBase is set
Returns Chain2
the chain
- Defined in ik/fabrik2.ts:544