Rig's movement limitations

[Anonymous]

Hi

I was wondering if the rigs do have some limitations related to their motion range or capabilities. For instance, do extensive stretching or bending of the character lead to geometry distortion and dislocation of its controllers? Should we be cautious on the degree of freedoms that we are supposed to bend FK/IK limbs or extend them? Is there a way to perform unlimited bending or stretching that will not cause any deformation or deregulation of geometry without worrying about messing with controllers?

Thanks

[jmreinhart]

"the rigs"? Are you asking about a specific rig?

There are always limits to how far you can stretch/bend/twist a rig, depending on how it's set up. A well designed rig will be able to do everything the animators require, but sometimes they still requires tools in addition to the rig, like sculpting tools to tweak an extreme pose in a specific shot.

rotatePlane IK will limit you to one degree of rotation on the middle joints (the elbow), but in my experience it's best to leave all 3 axis unlocked on the FK chain.

[Anonymous]

Is there a way to make rig's motion unlimited without geometry distortion or flipping? 

[Anonymous]

So are the pole vectors significant in trying to hinder geometry from flipping after 180 or -180 degrees?

[Anonymous]

The thing is that the rig I am using has IK in its legs and polar vectors in its knees. If I try to make an extreme movement (e.g. extent the legs in an acrobatic pose) the whole animation gets messy. The controllers are dislocating from feet and I have to chase them around the scene to grab her so I can move its legs. When I play the whole motion from frame 1, the legs are disorganised and do not evolve appropriately over time. What am I doing wrong?

[jmreinhart]

poleVectors are required to make the ik solver stable they do not affect the twist. The twist is normally done using a set of joints along the arm/leg that each twist a different amount.

Twisting past 180 degrees is very challenging because even though the animator interacts with the rig using Euler Rotations (which can easily be set to values outside -180 and 180), constraints and skinning deal with matrices. Matrices don't contain the Euler rotation values themselves just information to describe the end orientation. So to a matrix a rotations of 270 degrees on one axis is actually 90 degrees.

There are two main ways of avoiding that.

1. using the noFlip mode on orientConstraints which do keep track of the Euler Rotation but they will still break after a certain point and can give unstable results if you do looping playback.

2. Setting up the rig so that you get the twist from the actual channel box values the animator interacts with and never converting to a matrix at any point. That's the most stable method.

[Anonymous]

Please show steps of how to perform your last 2 suggestions.

Thanks

[jmreinhart]

Method 1 is explained here: https://vimeo.com/149066264

I can't provide a step-by-step tutorial for method 2 because it varies greatly depending on the rig.

[Anonymous]

I am using Gabriel Sala's Dana rig. It was made using Advanced Skeleton. How can I check if it has 360 degree rotation abilities or not?

[jmreinhart]

Twist the forearm 360 degrees and see if the mesh flips at 180.

[Anonymous]

I am not sure if it flips. But definitely what it does is that the upper arm gets thinner (geometry) when rotated 360

[jmreinhart]

That tends to happen. IF you look at that image I posted in a previous response you can see that twisting the joints tends to make the mesh lose volume and become thinner. You can use dualQuaternion weights, more twist-distribution joints, a corrective, or other systems to improve the deformation. Usually I would use a corrective.

[Anonymous]

corrective such as ?

[Anonymous]

I also get this curly tip toe feet whenever I drag the feet controllers. I am not doing that on purpose. How can I avoid it?

[Anonymous]

Dana rig gives me those turn around feet. I am not touching them. They end up alone and seems impossible to fix it. Can you guess what attribute should I tune to fix it? 

Thanks

[jmreinhart]

A corrective mean a corrective blendShape https://knowledge.autodesk.com/support/maya-lt/learn-explore/caas/CloudHelp/cloudhelp/2017/ENU/MayaL....

For the feet it's very hard to know what's causing the problem but I would guess that you have posed a control on the toe without noticing it. Unfortunately Dana is not a free rig so I can't ask you to send the scene file. Unless someone who has already bought the rig responds to this post that's the best advice that I can offer. You might be able to get an answer if you email the person who made the rig, but it to me it looks like you've just posed a control, the rig is working fine.

[Anonymous]

How do I check if I have posed a control? Not to my knowledge. I get those curly feet without touching them at all. 

[jmreinhart · Accepted solution]

You just have to check the controls in that area and see if you've accidentally set any values on them. advanceSkeleton is a very solid autorigger so it's really unlikely that the rig armature is broken. You could trying opening a new scene file with the character and posing her into that same pose to see if the foot messes up. It's also possible (but very unlikely) that you accidentally moved/rotated a joint instead of a control at some point, you'd need to go into the reference editor and check if something that isn't a control has been changed.

https://knowledge.autodesk.com/support/maya/learn-explore/caas/CloudHelp/cloudhelp/2018/ENU/Maya-Man....

That's really all the help I think I can give.