Reverse an IK Chain?

(Jon) #1

I’ve created a chain of bones for the body of a dragon and I want to move the head around using a section of the body as a fixed point from which all the bones up to the head pivot.

I would also like to move the tail around from the same point. The bone near the head is the base bone and when I move it the whole body moves. When I move the tail (with Auto IK on) I get the desired effect but I can’t work out how to place a pivot point down the body and get the head to move around. Is it necessary to have the bones pointing in a certain direction or can the IK solver work in reverse??

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(thelowlander) #2

don’t use auto IK for this. Set the chainlength on the IK constraint to the amount you want to use. (bones in your chain.) 0 resets it to go all the way to the root.

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(Jon) #3

I understand that part, but I’m trying to move the first bone in my chain (root bone) around as if the root were further UP the chain not further back in the chain. I’m starting to suspect a chain of bones can only behave in a unidirectional way depending on which way the tips of the bones in the chain are facing. Can someone tell me if the effect can be reversed?

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(pappy) #4

Here’s a simple armature that I think does what you want.

http://www.clipsandscripts.com/wip/blender/dragon_armature.blend

Pappy

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(thelowlander) #5

I think I know what you mean now and that is exactly what any IK constraint does when it has a target.
Look at pappy’s example. These are IK chains without targets. If you move the first bone in the chain (root) all the rest moves along.
If you add a new bone behind the tail, and target the last bone in the chain to it (fill in the target object>then bone field appears for armature>bone name)
it WILL do what you want. It will stay looking/stretching towards the target as you move the root around.

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(Jon) #6

Thanks for that. I don’t think it cleared up exactly what I was after but I ended up just redoing the armature with the bones facing the right direction to get the IK movements I need.

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