Follicles flipping in Maya 2016 SP1

[Anonymous]

I'm rigging a dinosaur skeleton.
To get the tail and neck bones to move correctly, I have them parent constrained to follicles, which are attached to a nurbs surface. The nurbs surface is bound to joints.

Unfortunately with some rotations, random follicles will flip out of their correct orientation, seemingly ignoring the normals of the nurbs surface. I've looked around online and it looks like this used to be a common problem, but most people are saying it was fixed around Maya 2011 or so.

Please find a link to a stripped down version of my scene below. The tail has been rotated down (using the stairs down attribute on what was the hips control), and you can see that a couple of follicles near the base and one further down aren't aligned properly.
Interestingly, if that attribute is at 0 and I use one of the other controls to rotate or bend the surface, the flipping doesn't occur as reliably - sometimes it doesn't happen at all, and other times it's a constant issue.

Has anyone encountered this or can see anything in my scene which might be causing it?

Thanks.

Link to scene: https://drive.google.com/open?id=0B2U9xMM1hDhra3NSM1pJcldNdGc

[mspeer · Accepted solution]

Hi!

There are a lot of relationships in your rig and it looks like some calculation errors happens caused by an error in Maya or by the formulas created by the concatenation of some nodes which result in invalid values.

My advice would be to use a quick and dirty workaround:

1. select aimCone1_aimConstraint1

2. Change Up Vector from 0 1 0 to something like 0 1 0.005 (Take one zero value off the calculations.)

You might need to increase the value if flipping happens again

[Anonymous]

Hey, thanks for your suggestion! I'll try that out to see if it helps relieve the symptoms.

I am interested in seeing if there's a more reliable fix though - I don't want to have to tell animators to go playing with the aim constraint if it starts flipping on them down the line.

[Anonymous]

So, your solution DID work and I'm therefore accepting it as the solution.... but I still don't know why or how it worked.....