[Rigging]Pivot point under a moving parent

[hiroober]

It’s probably a dumb question as I’m new to rigging, but I got stuck at this problem, just couldn’t figure out a solution.

I have this fore leg from a feline set up in the scene. Fairly simple as you can see in the screenshot. Several joints, corresponding IKs and a foot control. I need to set up rotation at the Wrist_Pivot group, and the pivot point should always be on the wrist joint as you can see as below.

But since it’s the child of foot_Ctrl, whenever I move the control, the pivot point shifts from that joint as you can see as below.

I understand it is the way parent/child works, but this is not what I need. Any advice/workaround?

Here is the link of the file if you’d like to have a play:
Foreleg_Rig.mb - Maya2016 file.

I’m dying to know how to do it!! Appreciate it!!

[CGMelanie]

I looked into your file and I am afraid what you are trying to do is either impossible or extremly hard.
At the moment you are already controlling the rotation of the wrist with an IK handle, on top of that you want to rotate the wrist pivot group to rotate the foot.
If you unparent it you loose the mechanic which bends the wrist if you lift the foot - if you would change the pivot of the foot CTRL you would also loose that mechanic.
You can ask yourself now a question you can either : Look for a complicated and long solution that will give you both mechanics or use another setup and loose the mechanic or keep it as it is and don’t have an additional input to rotate the wrist corretly.
For your specific setup I would recommend switching to a locator method - sure it

doesn’t give you that automatic wrist rotation but it is also not 100% necessary.
For the locator method you wolud simply delete the IKs, create 2 locators 1 at the position of the wrist and on of the paw joint, parent the wrist locator underneath the paw locator, make an IK handlefrom wrist to thigh and point constrain the IK to the wrist locator. Orient constrain the wrist joint to the paw locator.
If you now rotate the paw locator you either have the quadruped stand on is tip toes or not.(I added an additional locator to the paw_end that has an orient constrain on the paw)
I don’t know if this is exactly what you want but I hope I could help

[Horganovski]

For me the approach of running IK down 3 joints is rarely ideal, particularly for a cat leg where you need a lot of flexibility and control over the shape of the leg.

I’ve spent a lot of time thinking about quad legs and have developed my own version I use here which only ever has IK running down 2 joints at most. This video I made a while back doesn’t discuss how I rig it specifically but it discusses something a lot of people miss when rigging quad legs in my experience. Hope it might help illustrate :

[vimeo]232743975[/vimeo]
Cheers,
Brian

[hiroober]

For me the approach of running IK down 3 joints is rarely ideal, particularly for a cat leg where you need a lot of flexibility and control over the shape of the leg.

I’ve spent a lot of time thinking about quad legs and have developed my own version I use here which only ever has IK running down 2 joints at most. This video I made a while back doesn’t discuss how I rig it specifically but it discusses something a lot of people miss when rigging quad legs in my experience. Hope it might help illustrate :

[vimeo]232743975[/vimeo]
Cheers,
Brian

Hi Brian,

Thanks for the response! I find it very inspiring, I didn’t realise the problem you mentioned in the vid at all and I’m planning to have this set up in my rig. Well, if I could solve the current issue first…I so hope you have tutorials on how to build the quadruped rigging. But before that, I’m confused by seeing you mentioned the dog rig has “IK running down 2 joints”, then how to make the wrist bend inward like in your lion animation clip?

[oglu]

just in case you havnt seen the cult of rig latest stream…
those vids are fundamental for riggers… even i dont rigg at all i learn something every stream…

//youtu.be/_bT9Ji5v6Vg

[Horganovski]

Hi Brian,

Thanks for the response! I find it very inspiring, I didn’t realise the problem you mentioned in the vid at all and I’m planning to have this set up in my rig. Well, if I could solve the current issue first…I so hope you have tutorials on how to build the quadruped rigging. But before that, I’m confused by seeing you mentioned the dog rig has “IK running down 2 joints”, then how to make the wrist bend inward like in your lion animation clip?

I should clarify sorry - I mean I don’t have one IK node driving 3 joints, usually just two and then maybe a single chain IK or an aim constraint etc driving the other joints in the leg, as indeed you do need to be able to bend inward etc. My main point was that with one IK node driving 3 joints you lose a lot of finer control over the rotations of each joint in the chain in my experience.

[hiroober]

I looked into your file and I am afraid what you are trying to do is either impossible or extremly hard.
At the moment you are already controlling the rotation of the wrist with an IK handle, on top of that you want to rotate the wrist pivot group to rotate the foot.
If you unparent it you loose the mechanic which bends the wrist if you lift the foot - if you would change the pivot of the foot CTRL you would also loose that mechanic.
You can ask yourself now a question you can either : Look for a complicated and long solution that will give you both mechanics or use another setup and loose the mechanic or keep it as it is and don’t have an additional input to rotate the wrist corretly.
For your specific setup I would recommend switching to a locator method - sure it

doesn’t give you that automatic wrist rotation but it is also not 100% necessary.
For the locator method you wolud simply delete the IKs, create 2 locators 1 at the position of the wrist and on of the paw joint, parent the wrist locator underneath the paw locator, make an IK handlefrom wrist to thigh and point constrain the IK to the wrist locator. Orient constrain the wrist joint to the paw locator.
If you now rotate the paw locator you either have the quadruped stand on is tip toes or not.(I added an additional locator to the paw_end that has an orient constrain on the paw)
I don’t know if this is exactly what you want but I hope I could help

Hi CGMelanie, I sincerely appreciate your reply. After 3 days of having no access to Maya, I finally got the chance of sitting down and trying your method out. I quite like the locator idea, except for the fact the knee and wrist joint can’t keep straight as in my previously rig --I have a RP IK connect from thigh to knee, then manually shifted the IK effector’s pivot point to the wrist joint.

My goal is to keep the knee and wrist straight as default when moving the foot ctrl, but wrist and paw can have FK rotation, and wrist is the parent of the paw. Because as below illustration shows, except for the situation in 5, most of the time wrist and paw has FK rotation. When lifting the paw off the ground, it’ll be much easier and more efficient to have knee and wrist straightened as in 2, then animate the rotation of wrist and paw joint.

In order to achieve my goal, should I have a FK/IK set up as in a typical human arm rig?