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So I'm trying to set up a path constraint, bound to an IK, (like in the Stretchyman video).

I've created the path, created the IK bones, setup the IK constraint, binding the path to the IK bones, and created the path constraint targeting the small bones along the path. But when I move the IK target, it the path does not move with it, despite saying it it bound to the IK bones.

I assume I have something in the hierarchy out of order, but I'm unsure where.

Path constraint binding issue - YouTube

The order constraints are applied matters. You apply the path constraint, which positions the bones alone the path. Then you apply the IK constraint, which moves the bones that the path is weighted to. Since the path constraint has already been applied, the bones don't move to the new path position.

To fix this, drag the constraints in the tree to reorder them so that the path constraint happens after the IK constraint.
Constraints: Order

So when I drag the path constraint to happen after the IK constraint, now my IK target simply moves around, and doesn't affect the IK bones at all.

Below is a screen capture of what is occurring.

path constraint issue 2 - YouTube

That is odd. I can't tell what is happening from the video. If you can post the project file, that would help.

FWIW, attached is a simple project that works as expected.

It's hard to tell from the video, but it looks like "tail ik 1" is a child of "Tail 1". "Tail 1" is being affected by a path constraint so try moving "tail ik 1" to be a child of the root bone. I believe it should work then.

Tried adjusting the tail IK to be a child of the root bone, still no luck. Attached is the project file.

Thanks for taking the time guys!

VGG Right Rigged 2.2.spine

The rotate and translate mixes on your path constraint were zero. Setting them to 100%, it appears to work like you want.

You might consider setting up your path like this:
 Loading Image
Though I can't see your image so maybe that doesn't make sense. You may want 2 or more sets of IK bones (or just use 3+ bones without IK, it's probably easy enough to control) to control the path. Either way, straightening the bones and placing the handles and weights like in my pic will give your path reasonable bends. The further out you place the handles from their vertex, the bigger radius you get when the bone cause the path to bend.