How does one go rigging 180-360 turns without popping?

SummonedSpirit

Title says it all,

I'm trying to prepare a rig which can show a contortionist doing tricks. The model below is a test model and not the actual model which will be rigged before clothed. Is it possible to pull it off in 3d I would like the joints to maintain its volume while doing some extreme twist with the limbs ( feet turning 180-270 degrees) (Arms and hands turning 360 degrees)

 

Mark Dygert

Gimbal lock. You probably need to change the rotation order of the joints or controllers.
https://www.youtube.com/watch?v=zc8b2Jo7mno

SummonedSpirit

Ah I see Mark, thx! So if I understand it right the reason why the rig pops is because the rotation order isn't parent correctly and I'll have to change it to be able to do such a rotation. From the video you sent me, I understand that this parenting order will require change should the joint be rotated in another directional extreme.

As the person i'm rigging is someone with Ehlers Syndrome the person would be capable of rotating their foot 360, doing splits and over splits which might pop the rig I believe in some way. Perhaps is it possible for me to create an option in the rig to change the parenting structure of the rotation of the joint to fit the set of extreme movements the character does or would a completely seperate rig require creation for that function?

poopipe

You could use quaternion based controllers but animators usually whine about that.

Or... conventionally people will split the control across two nodes, Eg. one handling x/y and the other z. 

It's a common problem at shoulder joints so a bit of googling should show up some examples of solutions. 

SummonedSpirit

Alrighty Pipe i'll take a look this seems more complicated than I thought

RN

I think twisting happens when some vertices are moving while connected to other vertices that aren't moving.



If you try twisting a piece of fabric (try it on your sleeve), it does the same thing.
I don't think there's way around it, not without an additional loop cut around the middle with a corrective morph (aka blendshape, shapekey) to preserve volume.

PolyHertz

In the example image provided, the simplest solution would be to just detach the foot and have it rotate by itself instead of with the pants leg, then the geometry wouldn't collapse inward while rotating it.

Olli.

add more geo bones!
The way ive solved issues like this in the past is by adding a chain of twist helper bones inside the arm (or leg in your case)

here's the best image i could find on google, I dont have any of my rigs handy at the moment.
https://imgur.com/rQV1eGE
I've circled the helper bones with red, and the bones themselves are also red.

Its basically 3 or 4 bones that go along the inside of the main limb bone, and their Y rotation value is linked to the wrist (or foot in your case), rotating less the further from the extremity they go.

This lets you spread out the twist along the whole length of the extremity. You will also need to have sufficient geometry on the mesh to support the rotation, or youll get the same effect as in RNs gif, but at least the mesh in the OP should be dense enough. The problem there is just that the whole twist is being applied in like a 10cm area of the leg, so there isnt enough geometry to support it.