Cage, I'll have a look at VK's stuff when I can find a bit of time. I may be wrong, but from memory in that thread VK was talking about animating the joint center, changing it over time, the chain link problem is not an animation problem, it requires two different joint centers - at the same time! Anyway I think that's what it was about, but I'll take another look.

markschum said, quote: "I know a few people have tried extra bones between links but I could never get that to work."

I think that is the most promising path to a solution, 'ghost actors' as I call them. Perhaps I am missing something, but in my imagination it would not be hard to implement in principle. In practice it would require a lot of work, too much for it to be an attractive proposition to do it by hand for anything beyond a two or three links, but if we are talking a python implementation a two or three link example should be enough.

I must strongly disagree with the position of the origin as suggested in nruddock's  diagram. It will be the best position for one rotation, but the worst for the other. I'll make a diagram of my own to explain why. I believe that the best place for the origin is where the two inner surfaces of the links meet, as per my earlier diagram. However if combined with markschum's idea of extra bones (ghost actors), then nruddock's position does become important as the foci of one rotation, as we could then use two joint centers for each link and have each at its optimal location.

I will try building a short chain with ghost actors, in the hope that you can do a python implementation to do longer chains.

I think pitting the chain-building into a separate script, is a good idea.

I would still like to send you my chain, as I think the problems would be easier to understand if you had a working example. However I don't know where to send it to.