Bezier IK using in rubberhose style rigging creates a knot

[hiroober]

Greetings, lovely people! I'm been scratching my head for more than a week, and just couldn't get it solved. I'm hoping I can have some help from the forum.

I'm rigging a dancing figure, I need the arms to be quite flexible, e.g. able to have the elbows go to both directions smoothly, so I assume the regular IK is not a good choice. I didn't use FK as it is quite a time-consuming way to animate. I got them set up using rubber hose style via Bezier IK like how it's shown in "DUIK QuickTip#05 Rubber Limb" from Rainbox Production channel on YTB). However, I found if I drag the "pole" of the elbow(aka Arm|Curve in Duik system) to a certain distance, it snaps to a knot. I've tried to rebuild the curve for more than half a dozen times, the problem is reproduced. I found the issue seems to be orientation-constraint on the elbow pin. If there's no orientation-constraint applied, no matter how to animate the arm curve, I won't have this issue, but if it's a rubber hose style, I do need that constraint to keep it a smooth bezier curve.






I'm on AE2018/Duik v16.2.7

I appreciate any help in advance.

[hiroober]

Here's the project file.
https://gofile.io/?c=ap15P3

[Duduf]

Hi, I'll have a look at that, I think the orientation constraint has issues with the way Bézier IK are computed.

BUT, in the quicktip, it's a standard IK and it works well, do you really need a Bézier IK?

Also, thinking FK is more time consuming than IK is a big mistake, but you'll discover that by yourself when gaining experience

[hiroober]

Hi, I'll have a look at that, I think the orientation constraint has issues with the way Bézier IK are computed.

BUT, in the quicktip, it's a standard IK and it works well, do you really need a Bézier IK?

Also, thinking FK is more time consuming than IK is a big mistake, but you'll discover that by yourself when gaining experience

Thank you so much for your reply Duduf! Actually I tried FK, but found there're some movements that can be achieved neither IK nor FK. That's why I thought Bezier IK might be the solution. Here's an example, quite a simple movement of having an arm bending in front of the body then stretching upward.


I might have missed something here, but I simply couldn't get it done in FK/IK set-up. Bezier IK seems to be the solution as I could animate the Arm|Curve and the wrist ctrl to get to the position, but then I got stuck at the knot issue. I'd really appreciate it if anybody could direct me to the right direction.

[Duduf]

I do not see why it would not be possible in FK?

And in IK you'd have to animate the "reverse" checkbox and probably the stretch value too.

I'll have a look at the orientation constrait to see how this unwanted rotation can be modified, but with an orientation constraint you necesasarily have a bump smewhere.
Maybe you could use the connector instead to automate the rotation of the elbow