Cineversity

Hi Dr. Sassi,  I was hoping you could answer this for me as I’ve seen in another post that helped with:(https://www.cineversity.com/forum/viewthread/2334/#8862).

My dilemma is, I have a character thats similar to that and I’m using spline ik for the legs & arms, I’ve now set the pole vectors for the legs to use X for right leg and -X for left leg (originally I had them set to “auto” but when I did a render they flipped all over the place), except now I’m finding that when I render out a hardware render with the R_leg Pole set to X it flips in the viewport but renders fine… and by setting it to -X is fine in the viewport but renders flipped.

There seems to be something weird going on between what I see in the viewport and what renders out, did you have any ideas?

I’ve attached the scene file stripped back to the bare elements.

Cheers,
Jody

Hi Jody,

Please have a look at the file. The Pole has a new position and the Axis (IK) is set to -Y.

Scene file and render test clip (screen capture):
https://www.amazon.com/clouddrive/share/taMRU82oRbmBetdYMXUTPLboNVCIBQsnEZhs3Phhftx
Please advice if that file can stay online or if you like to have it not public.

To your problem, I was able to see how different each render “digest” the set up and the flip of the knee happens in your file. I would expect that there is no such difference among the renders, but here we met one of such cases.  You might check with the support, but I guess, it is a safe bet, that this flipping indicates something that reminds me on the Euler Angle, not something that should be left alone. My advice would be, setting up the Pole and the Axis differently as in the example file (attachment above) and perhaps fine tune it even more. I’m not certain if the proximity of the B-Spline point #1 and the Pole (in your submitted file) re the reason for that. I have to explore it a little bit more. Explore means here, to make a predicable failure among the renderings, and advice in a better way.

Please let me know if the current set up works for the right leg.

All the best

Ahh, thanks you so much, changing it to -Y and moving the pole has worked - I had try other settings but failed to move the pole when I did. I’ll need to keep an eye on the legs for all my other 2d characters that currently have it set to X, I’ve animated quite a few now and its really only happened to this one so far but he does have his leg up quite high on the bin.
Cheers,
Jody

You’re welcome, Jody.

The Axis is more an added idea, the pole and its relation to the goal is the most important part here.

I think the best indicator is to have the IK line (green) and the Pole line (lilac) not or not close to a straight line. If both line up in a straight line, the IK flipping can happen with a great probability.
https://www.amazon.com/clouddrive/share/cB9U3e0d7zFOJUPyT5x7bmEIUHHV56Td7ILdrQAQQNN

Well, it is a little bit more complex than that, and the illustrations in the manual are quite good, so I might suggest to just have a look at them.
https://help.maxon.net/us/#TCAIK-ID_TAGPROPERTIES
To have that disc in mind is a good help to get things working, e.g., the Twist parameter.

I hope that is the fastest way to give you a good feeling about your set up.

A short little tutorial is here (including the next part).
https://www.cineversity.com/vidplaylist/character_rigging_in_r12/character_rigging_in_r12_leg_ik
Pretty much on the end.

My best wishes