3
$\begingroup$

I have an IK chain controlling a mesh. I want to attach this IK chain to something. I have tried putting Child Of, Copy Loc, and Copy Transform bone constraints on the start of the chain. None of them do anything. Is there some rule against using constraints on the first bone in a chain? I notice that it works if I constrain the bone in Edit mode with a regular constraint instead of a bone constraint in pose mode, but this causes some strange issues.

Anybody know how I can go about attaching my bone chain? Specifically, I need to have it following a specific vertex (vertex group) on a mesh that is being simmed, so it doesn't work to constrain the entire armature object, or to constrain to the object. Is there an option better than constraining the bone in edit mode to an empty, and then having that empty be constrained to a vertex?

EDIT: Example file (see comments)

Improve this question
$\endgroup$
19
  • $\begingroup$ do you have other constraints on that bone ? $\endgroup$
    – Chebhou
    Mar 22, 2015 at 21:13
  • $\begingroup$ Yes, I have IK pointing to a vertex group at the bone's tip, but the problem remains even if I disable it. I have found that it works fine to constraint a bone to a vertex group with the constraints listed above if the bone is a single bone, or if the bone is part of a chain. But not if the bone is the head of the chain. For example, I can Child Of a bone to a vertex group at it's head, and IK it to one at it's tail. This causes the bone to move as the mesh it is constrained to moves. But it doesn't work on bones at the start of a chain. $\endgroup$
    – Ascalon
    Mar 22, 2015 at 21:17
  • $\begingroup$ do you want both head and tail of the chain to keep following the vertex group ? if this is the case parent the IK target to the vertex group as well $\endgroup$
    – Chebhou
    Mar 22, 2015 at 21:18
  • $\begingroup$ I'm using this specific rig to transfer motion from a simple cloth simmed mesh to a more complex final mesh. So in this case, every bone in the chain is IK'd to a vertex at its tip, and Connected to the bone above it in the chain. But as the cloth object moves (clothing on a character that is moving), the top bone in the chain gets left behind because it's head isn't attached (only its tail through IK.) I need to attach it to the mesh. However, the problem I am describing appears to happen with any sort of bone chain, not just this strange setup I have. $\endgroup$
    – Ascalon
    Mar 22, 2015 at 21:21
  • $\begingroup$ can you add the bone chain and the cloth picture ,or a sample file , i can't get the full picture :) $\endgroup$
    – Chebhou
    Mar 22, 2015 at 21:25

1 Answer 1

Reset to default
2
$\begingroup$

The issue was with the bone at the start of the chain being set as Connected. This is because the bone chain was made using the Skin modifier on a vertex chain. Normally if you add a bone and then extrude it to make a chain, the first bone is not Connected. Apparently the armatures made by Skin are. The Connected checkbox is greyed out, but still can be unchecked. Since the bone has no Parent, the Connected status was locking it in place.

Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.