Joint Pinning - Elbows and Knees

#1

I need help finding a solution to pinning the joint of a 2d chain. Ultimately, so I can lean on the elbows and knees of a character.

Anything would be helpful right now. Thank you.

#2

This may not be standard practice but it’s what I was once taught and very useful for everything and goes well beyond just locking down elbows.

First things first do whatever animation you do up to the poit. This setup is done while animating and requires that you are comfortable with constraints. I’ll explain the steps based on the numbers in the image below.

  1. The base rig, however it is set up, is animated and you have reached the pose that, as per your own example, needs the elbow locked down. I then go and turn on snap to points and make sure under the snap to point menu that centers is checked on. This is the easiest way to match the rigs.

  2. Draw the 2 bone chain from the base of the shoulder bone to the elbow with snapping on to match the joints. (if the joints aren’t matched perfectly try to draw the new joints from root to root)

NOTE You can draw the bones in the opposite direction but this places the constraints in opposite locations and can be a little more annoying to work with.

  1. With constraint Compensation on (see the button in red) POSE constrain the old arm rig (shoulder and upper arm) to the new one. Nothing should pop or shift if you did this right.

  2. We now have the begginings of a new 2 bone ik chain that you can lock anywhere. Now you need to position constrain the effector of the new rig to the IK control of your choice (see the circle) and the arm and shoulder should now move as if they are connected like an arm. (thats what all those picture badly show :P)

  3. Constrain the orientation of the forearm to the circle as well so it doesn’t shift around (match the orientation of the circle or control object to the forearm first to avoid any popping). ALSO parent the new rig to the same object that the old shoulder was parented to, in this case the upper spine bone.

  4. Finally key your constraints on that frame (the pose constraints and the orient and position constraints) and also key or blend them off properly at an earlier point. You can continue to animate the rest of the body as you wish and the elbow will be locked in place until you turn your constraints back off.

you can also add in an up vector or roll control if you really need to

Sorry it’s so long but this is the best solution I have found… You definately need to be comfortable with constraints to do this quickly but I did it in a few minutes and have always found it well worth the effort. Especially since it is non destructive to your origional rig.

i’ve also used this to create inversed spine rigs, locking knees, and dangling a character from a limb (drawing a chain from the hand all the way down the body and animating it with FK as an example.)

#3

thanks, Jesse.

I’ve found that elbow pinning really isn’t necessary ( I say that now… ). Elbow placement is made from the relationship between the shoulder and wrist. I need a solution that’s modular and transportable. I need it for more than one scene, and want to blend it on and off. I’m slowly getting a solution.

#4

heh heh, fair enough… though you could simply leave this as part of the rig and blend it on and off. But if you’ve found something that better suits your needs, good on ya and if ya have the chance to share I’d love to hear about it.

#5

Hey Jesse!
How’ve you been? Real shame I missed you when I stopped by the school a couple of month back :frowning:

#6

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