• Adobe After Effects Expressions

  IK in 3D, strange anomaly

  Posted by Ben Pohl on April 6, 2015 at 4:57 pm

  Hey all,

  I’ve been using DUIK for years with happy results.
  I’m trying to use DUIK to drive some IK in 3D and I’m getting a strange result. I think there’s probably a simple fix but I’m stumped.

  I’m using DUIK to drive a simple leg in Element3D. Everything works fine until I parent the controller null, and the root null, to a master null.

  Here’s a quick screencap of what’s happening:
  https://youtu.be/x-7K68caB2Q

  I’ve tried the same setup with just shape layers in 3D without Element, and getting the same result. So I know it’s not Element.

  Any insight is appreciated.
  Thanks!

  Ben

  Matthew Lincoln replied 8 years, 11 months ago 4 Members · 5 Replies
• 5 Replies

• 

  Logan King

  April 7, 2015 at 2:36 am

  Have you tried switching to the layer effects control & turning on the Orientation Checkbox ?
• 

  Ben Pohl

  April 7, 2015 at 1:23 pm

  Hi Logan,

  Yeah, all that does is flip the orientation of the knee. The foot is still floating away from where it should be.
• 

  Eric Epstein

  April 7, 2015 at 4:00 pm

  Hello,

  Good idea using Element like this.

  I don’t know why this happens exactly. But my workaround was to simply not parent it, and connect the top of the chain to the body via expression.

  Lets say the upper leg is parented to a null called ‘hipA’ and also there is a ‘hipB’ parented to the body.
  I’d use the following expression on the position of ‘hipA’
  L = thisComp.layer(“hipB”);
  L.toWorld(L.anchorPoint)

  Additionally, you can use the expression below on the orientation of ‘hipA’ to have that chain auto orient to a free-floating ‘foot’ null.

  Hope that helps. -eric

  q=lookAt(thisComp.layer("foot").transform.position, position);
[q[0],q[1],value[2]]
• 

  Logan King

  April 8, 2015 at 1:58 am

  I would try what Eric said.

  I face this weird problem in 3D max at times and generally I re do the rig when it occurs there.
• 

  Matthew Lincoln

  May 16, 2017 at 7:05 pm

  Was this ever solved conclusively? I’m having a similar issue which I believe stems from the notion that DUIK is meant to only work in two dimensions.

  I’ve got a 3D element robot rigged to walk, and the legs each move relative to the robots body only in those two dimensions. But the moment I rotate the body or move a foot controller in z space, the IK starts to misbehave.

  If anyone did find a solution for 3D parenting and DUIK, I would be very interested to hear.

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