Stretchy spline IK twisting

[Steve Davy]

Just set up a pretty straightforward cable rig with stretchy spline IK, using this tutorial.

Works great, but it's part of a larger rig, which when rotated causes some unwanted twisting on the end of the IK spline. I've experimented with various settings in the advanced twist rollout of the IK handle, but have not been able to find anything that stops this happening. 

Anyone got any pointers?

http://tutnuts.blogspot.se/2010/04/stretchy-spine-rig-with-spline-ik-maya.html

How to Rig a Stretchy Spine with Spline IK in Maya - Rigging Tutorial tutnuts.blogspot.se This is a simple tutorial illustrating how to setup a stretchy spine with the maya Ik spline handle tool. Step 1) Create a joint chain. I ...

[Stephen]

Just skimmed the tutorial ( and it's constant ads to update my account to enable 3rd party hosting).  And I didn't see it mention anything about twist 

 In any case. On the ik handle you can turn on "advanced twist options" 

  And then below that you get a bunch of options and variables 

  I almost always use object rotation start / end  and use the first and last controls as the "objects" 

 And basically that means the control objects at the head and tail of the ik spline chain will tell them ik handle which way to aim.   

 You may have to play with the axis to get what you want 

 But the majority of the time is y as the primary and z as the secondary axis. And then what ever makes the most sense for your control objects 

 One major caveat. Is that the chain should always have x down the length of the joints.   If not. It still seems to be a bug that makes none of the twist options work 

Hth 

-=s 

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[Steve Davy]

hi Steve

Yes, there's nothing in the tutorial about dealing with twisting.

You definitely mean object start/end and not object rotation start/end, right?

In any case, I think I've tried every combination and nothing gets a good result. Either the end of the curve is oriented correctly but I have terrible twisting in the rest of the chain, or the chain is good but the end is not oriented correctly.

The IK rig itself is parented into another hierarchy (via the locators that are the controllers), and this is being rotated in worldspace quite extremely. Could that be the issue? I don't know how much curve normals influence a spline IK setup.

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From: maya...@googlegroups.com <maya...@googlegroups.com> on behalf of Stephen <stephe...@gmail.com>
Sent: Tuesday, July 18, 2017 6:45 AM
To: maya...@googlegroups.com
Subject: Re: [maya_he3d] Stretchy spline IK twisting

 

[Phinnaeus OConnor]

Hi Laura, once Michael has approved the extra time sheet days, how soon can your accounts pay me?

Cheers

Phin

 

https://phinnaeus.wixsite.com/phino

www.linkedin.com/in/phinnaeus

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From: Steve Davy <stevi...@hotmail.com>
To: "maya...@googlegroups.com" <maya...@googlegroups.com>
Sent: Wednesday, 19 July 2017, 3:33

[Phinnaeus OConnor]

Sorry guys wrong address! Not sure how that happened!

 

https://phinnaeus.wixsite.com/phino

www.linkedin.com/in/phinnaeus

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From: 'Phinnaeus OConnor' via maya_he3d <maya...@googlegroups.com>
To: "maya...@googlegroups.com" <maya...@googlegroups.com>
Sent: Wednesday, 19 July 2017, 10:46

[Stephen]

No worries the paper work has already been approved.

Steve , sounds like the controls for the ends are not aligned to each other.
Be sure to show their local rotation axis as well as the spline joints to get a better idea of what is going on
Or just parent constrain some locators to the controls and use them for the rotations.

If you don't need twist. You can also just stick a locator off to the side and use that as an up angle object

[Steve Davy]

You mean you actually get paid for doing this $h*t? 😃

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From: 'Phinnaeus OConnor' via maya_he3d <maya...@googlegroups.com>

Sent: Tuesday, July 18, 2017 5:49 PM

[Steve Davy]

Steve,

I think maybe I see what the problem is now.

The controllers are actually locators. They have clusters constrained to them, so any kind of rotation is redundant and they are thus not oriented with the joints. I've been using these as the aim/vector controllers for the twist attrs, but I assume orientation with the joints is necessary to get the correct result. I'll play with this a bit more. 

I definitely don't need -- or want -- any twist. That's really the problem 😉

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From: maya...@googlegroups.com <maya...@googlegroups.com> on behalf of Stephen <stephe...@gmail.com>

Sent: Wednesday, July 19, 2017 6:14 AM

To: maya...@googlegroups.com
Subject: Re: [maya_he3d] Stretchy spline IK twisting

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