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kingcoma

IK-spline: joints twist

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Yes. I'm yet again annoyed about an IK-spline. Probably has to do with me and the fact I'm at rigging =D

 

Anyway, here's my problem: I've made a character with 4 tentacles, and they all need to move. No problem, slap in a spline, bunch of nulls, an IK-spline and presto!

It works actually pretty good, except for the fact that some joints (randomly) start twisting when I either scrub the timeline, or start moving nulls around. I can manually fix this by rotating each joint, but that's time-consuming and unnecessary. 

 

Probably has something to do with poles or banking? I really don't know, hope you guys have some tips or tricks for me!

Attached a screenshot of a tentacle when I open the file (an animation) and a screenshot when I scrubbed the timeline a couple of times. Also the setup of my IK spline.

 

Thanks in advance!

start-joints-alligned.thumb.jpg.ebf04b0e380e1c15af2257d91d68e183.jpgafter-scrubbing-timeline.thumb.jpg.b6ded7956c7f19a37d64e42114f21507.jpgtentacle-setup-IKspline.thumb.jpg.3069ec8afc7140e2b7e86f1a86c920df.jpg

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Would be easier with scene file but educated guess is that joint axes are not setup properly. Try setting Z axis to point down the chain since that is the axis from which others are calculated. If not, then I would need a reduced version of the scene 🙂

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tell me about it... been loosing my mind this entire saturday wondering why stuff doesn't work as i expect it to... rigging can be really frustrating at times. but i think i got everything sorted now. well i thought that already a couple of times today, so fingers crossed.

 

regarding your problem: it's not necessarily only the joints axis, spline ik is also picky about the orientation of everything that's somehow in relation to it. but yeah, a file would certainly help.

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Have you tried doing an up vector constraint alongside the IK Spline?
The thing is you almost always need an up vector constraint to stabilize any kind of twist not only for c4d but for other software as well unless the twist is just a clear direct 1 to 1 set-up, which IK Spline is not by the way. 

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  • Thanks for the replies guys! Didn't have time this weekend (working) but here's the file of the character I was talking about.

     

     

    binnie rig upload.c4d.zip

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    Just curious, did you solve it? What was the issue?

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