Hi Everybody,
Does anyone know how to properly place and correctly setup a double knee joint solution in Maya?
I’m very much interested in the placement bit as I’d like to script the whole thing and add it to an auto skeleton procedure I have got.
Thanks a lot in advance :):
There are some ways artists doing it, but a very simple and solid one is using 2 IK rigs and blend them properly, your master control will be the lower one and the top one would be constrained in a correct way using the ratio you want, and you can add some top nodes over it for offsetting or different purposes. I’ve seen others doing it in a different way and due to their animator preferences … but this way you got much more control and there are alot of features that can be added to such a sys. Also you can add FK setup to the sys whenever you need rotate joints in lower angles for siting and such poses.
Let me know if you need more info,
Best.
Hi there,
thanks a lot for getting back to me so early.
mmm not sure if I got what you mean.You mean a double Ik handle and treating them as two limbs in one?. Would it be possible for you to produce a maya scene file or either jpeg with the scheme about this mechanism? It would be ace to be able to see it, I have troubles trying to visualize it 
perhaps I’m getting old
In the past what I did, as I always like to have a deformation skeleton and the animation rig, it was to have FK and IK driving a resulting chain into the animation rig and the resulting chain knee was driving via nodes the double knee in the deformation skeleton, by giving half resulting rotation to each of them.
Another thing I would like to know how to make right, is the joint placement if containing a double knee solution… How to place the leg chain properly? Should I calculate the position placing an ipothetical 3 bones chain and then determining where to place the double joint? To increase the changes to have a better behaving mechanism as an outcome I mean…
Thanks a lot and hope not to make a mess with this second message eheh
Not sure I follow either of these posts. What are you defining as a double knee? Like are you referring to a quadruped type leg set up(Which I know isn’t a double knee but people call it that)?(http://www.youtube.com/watch?v=VOt-Ew9tTns) Or are you looking for two joints over the knee where one rotates half of the other for better deformation of the knee when the leg is bending? Or the type where there is a small extra link chain between the thigh and the shin for the knee? (http://www.youtube.com/watch?v=yDZL1neQlds) Or something else? Is there an example you can show maybe?
Hi Sean,
Yep I meant a biped solution like the one in the video you just spot it. I am trying to understand which is the best way to do it, trying to keep thing rock solid and taking in account I have not a straight leg but something already modelled in a slightly bent position 
Thanks for the nide video btw
Does that video start to tell you what you are looking for? Or are you still looking for more information like how to set the IK up for it?
Also what is it you are trying to do with the rig as far as animation and purposes, and how advanced would you say you are in rigging?
I think I can define myself as an upper intermediate, not entirely sure, might be lower or higher. This is a tricky question
Regarding my plans, I am just trying to develop a nice deforming skeleton driven by the animation rig and I would like to include a correct double knee feature I never used before{I think the video you just posted answer my question almost entirely :-)}… As I have different characters of same size I will always use the same deformation skeleton and swap it as reference inside my animation rig file.
Do you have any reccomendations due to my pipeline?
thanks a lot
I would personally avoid using a double-knee. I would parent a joint or two under the knee and use something like Driven Keys to create any volume-preserving or sliding effects.
That can still be scripted and later it can be separately edited, and it keeps the base skeleton nice and simple.
It’s also nice to layer your special features like this, so you can easily remove them to create light-weight versions of your rigs, or easily swap out things for custom versions of the rig. (sometimes layering just gets overly complicated though, so your mileage may vary.)
(Edit: re-read your 2nd post, and it sounds like this is what you were doing anyway.)
The double knee is pretty simple. It’s just the joint chain you saw with an IK from hip to ankle. But I might agree with clesage, and just use a second knee joint over the regular one that rotates just half of what the regular one does (So set up three joints for the leg like usual, then duplicate the knee and delete the extra ankle so it’s still parented under the hip.) You can edit this more as needed, especially if you’re using it between multiple characters.
The only time I might recommend using the double knee is if you’re trying to rig up something to look as hyper-realistic as possible where you need anatomy to match real anatomy as much as possible. But even then you get into issues like in that video, where he’s trying to use motion capture information with that rig, and a motion capture rig can’t capture a double knee, so there are some translation issues still.
Using a double knee is like saying you need one joint for every vertebrae in the human spine because you’re trying to get the most realistic motion possible. If you are hand animating this stuff, you will probably never see the difference. It’s more about getting that sort of human motion that the eye doesn’t look at and go, no, no no, something looks off, but I can’t put my finger on it. That’s fake. But if you’re planing the kind of rig where you sculpt the bones and muscles to help deform it, then yeah, go double knee.
Sorry for the very late reply
Yep I will do like you said regarding the setup. Actually it is what I am always doing already for my elbows and will also do for the knees then
A big thanks to everybody who answered me here in this post and helped me.
I will probably bother you all again soon with another post 