Adding IK controls to existing rig causes joints to lock in straight line

[ecarlsenmedia]

Hi all, I'm trying to add IK to a dinosaur rig we bought from TurboSquid, which currently has no IK set up. I'm not super experienced in rigging. When I try to create an IK chain, i.e. on its legs or its long neck, the contained bones lock into a straight line. I can move the new IK handle, but all the contained bones stay locked in a straight line even when moving it. Any ideas how I can troubleshoot this? I'd prefer to not have to rebind the skin as it already has good skin weights. I've attached images showing its original state, what it looks like when I try to make an IK chain on the neck, and the same for one of the legs. Thanks in advance for any advice!

[hamsterHamster]

I'd say, it is likely joints orientation and preferredAngle related, try setting something in the fields to see if it has any effect.

If it doesn't give an idea how to tackle all other limbs, send the scene, zipped MA. Can be skeleton without the skin.

[Kahylan]

Hi!

As @hamsterHamster mentioned, it's likely related tp preferred angle or even just joint orientation in general.

Also for joint chains like the Neck that should gradually bend over the whole length instead of bending at one defined point you usually take an "IK Spline Handle" which calculates over a curve instead of a normal IK Handle with a Rotate Plane or Single Chain Solver.

[ecarlsenmedia]

Ah you're totally right. Unfortunately looks like all of the joint orients and preferred angles are set to zero 😞 When I create an IK handle, I'm able to start to get things looking better by tinkering with the joint orients, which gradually gets things to bend appropriately. But obviously very tedious and not super precise, basically eyeballing. Is there some sort of way to have Maya calculate what those joint orients should be automatically?

[ecarlsenmedia]

Hey Kahylan thanks for the tip about the IK Spline Handle. I tried it out and I'm thinking a regular IK Control may be better for my needs, as I want to be able to animate the dino's head and have the neck follow, i.e. lifting its head to take a bite from a tree before bringing its head back down.

[hamsterHamster · Accepted solution]

I doubt it needs such a precision for the elbow/knee cases.. give just some approximate hint so that the IK solver understands desired axis and direction. Where more precise definitions are required, are IK chains with more than two bones, which MIGHT be your case, yet - without seeing the skeleton and setup requirements - too much space for speculations.
Can't think of anything automatic, unless you want to set existing angles as preferred. See Rigging > Skeleton > SetPreferredAngle [options], where you can choose between selection and hierarchy.

[ecarlsenmedia]

Yes! You've made my day, thank you! "Set Preferred Angle" was exactly what I needed - I did that with hierarchy, and now the IK works without a hitch for the legs and neck/head. Very much appreciated. 🙏