joint orientation when mirroring

[cal...@glassworksamsterdam.nl]

I've got a question about joints and rigging. Sorry in advance if this is  a nooby question...

I've noticed that when you mirror joints (say left arm to right arm), the joint orientation flips. I've been told that it's good practice to have X point down the joint and Y and Z as dot products of that. However, when mirrored this is no longer the case as X now points in the oposite direction. 

What's the best thing to do in this situation? Change the joint orientation or leave it? It seems to effect the way in which the joints rotate, and could also affect fk/ik switching. Tip and suggestions would be appreciated. :)

Callum

[mikael persson]

I don't ever dive that deep as in creating my own FK/IK switches. I've just been focusing on functionality. If I rotate my shoulder x degrees for it to lift, I prefer to have the same values on both sides creating the same motion. That way it's easy to flip.

But I imagine you'll be having control nodes affecting the actual motion of the joints anyway? So mirroring and such will be dealt with elsewhere. There are so many tools nowadays that help you with this setup so you rarely need to care that much. Unless you want to learn from the ground up?

The reason to switch around the joint orientation is to avoid gimbals. But you need someone a bit more technical than me to actually explain that in full :)

Mikael

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[cal...@glassworksamsterdam.nl]

Thanks Mikael, it's good to hear your take on it. I totally see the point in being able to apply the same values on each side and get the same result. So rotating the shoulder +10 in Z makes it rotate up on both sides.

That's a good argument for leaving it the same. 

What tools do you use for your Ik/fk switching?

[mikael persson]

Unfortunately I don't have just one tool for the switching. But when that comes in question it's mostly a creature that needs animation and then I use one of the many rig builder tools out there. My favourite is:

https://github.com/nilouco/dpAutoRigSystem

This one is completely free, very flexible and has plenty of functionality. The main drawback with it is that you don't have a standard skeleton hierarchy included, or a single joint hierarchy as some call it. Rather it's broken up into separate joints but all of that is taken care of by the rig system.

Should you want a standard hierarchy you need to create it yourself and connect that to the rig yourself.

Then you have the advanced skeleton rig system, but that is crazy expensive if you are going to use it professionally. I really like their rigs though as they are fast and easy to use.

In my current project we are using Rapid Rigger, a first time for me. It's not that expensive but it feels slow in comparison to dpAutoRig.

Then you have the ancient dinousars like zooCST which is included in the CGM toolbox.

Feel free to ask more if you need additional pointers!

Mikael

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[mikael persson]

I forgot to add one of the recent additions to our toolbox. Studio library!

http://www.studiolibrary.com/home

A great tool for pose saving and mirroring.

[cal...@glassworksamsterdam.nl]

Thanks so much for sharing your workflow. I personally want to avoid auto rigging systems, for various reasons but I can see the advantages too. The main question for me is what people's preferred workflow is for joint orientation and obviously autorigging systems will have their own default setup, but I wonder what most riggers prefer when they make their own.

The links are very useful, cheer mikael.

[Borna B]

It is good pratice to have joint aim-axis, the one that points down to next joint, as X-Axis and most rigs are set up this way. But when you mirror you have 2 options:  Beahvior and Orientation. If you want your rig to function normally, in most cases, especially if it is humanoid rig than Behaviour mirror is okej and newly created joints will in fact have their X-Axis flipped to negative but it is normal and you get the desired effect - mirrored transformations. So you do not have to re-orient mirrored joints, you just have to correctly orient starting joint chain which will be mirrored.

Hope that helps.

On Fri, Jun 29, 2018 at 5:02 PM <cal...@glassworksamsterdam.nl> wrote:

Thanks so much for sharing your workflow. I personally want to avoid auto rigging systems, for various reasons but I can see the advantages too. The main question for me is what people's preferred workflow is for joint orientation and obviously autorigging systems will have their own default setup, but I wonder what most riggers prefer when they make their own.

The links are very useful, cheer mikael.

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Borna Berc

[Anthony Enos]

As far as the joint orientations, you may want to take a look at some of the systems out there and see how they handle it for reference. From what I can see, Maya's own Human IK, and Advanced Skeleton leave the mirroring as is. Based on that alone, I think the chances are you're better off leaving the joint orientations as they are after mirroring, unless your have a well trusted expert rigger telling you otherwise. (I've done some rigging, but it's an area of expertise for me) Though the auto rigging systems may be a "dummy" way for all of us to rig, there's been a ton of thought behind them, so I'd be surprised if they were fundamentally incorrect. Character animators really like things to work the way they expect. For someone like me that's more of a generalist, existing automated solutions are best way to go. Inevitably, you may find yourself needing to rig a dozen characters in a short time and have no other option. All that said knowing how it all works under the hood is still very important to be able to customize the tools.

Don't wont to drag you too far off topic, but I second the Studio Library recommendation. The team of animators I was working with seemed to like it for our purposes on Pearl. We made rigs using Advanced Skeleton (with some additional customization on top), anim school picker for controller selection UI (better than the name would suggest), and Studio Library was used for sharing of pose and animation clips. We had to get a bunch of preliminary rigs handed off really quickly, and all of the tools managed to get integrated and continually updated during production. As to the cost of Advanced Skeleton, the license is $3K for a studio, but for an unlimited site license with no seat limit. It can be worth it for the right project/studio. It's $750 for a freelancer.  The support was surprisingly responsive, and there were updates made specifically to fix our bug requests during production. Like anything else, not perfect, but good. I may check out dpAutoRig myself. Hope there was something useful in my rambling on the subject.

[stephenkmann]

yup, mirror with "behavior" for arms.. 

 but then I flip the local rotate axis and run joint -e -zso; to get the X trans to be positive , then flip the orientation back to behavior so you get the correct behavior. 

  This is mainly due to wanting to build stretchy arm systems and I'd rather move positive X and have that mirrored for arm to arm

of course. that depends on if you are building the rig system off the joints, or just controlling them and don't care about their oreintations. 

 as for IK/FK i've been using the built in system since maya 2015, and other than a  few stumbles in the very first dot releases that year, it has proved very reliable.  ( FK is just an hierarchy match to the IK, rather than multiple sets of joint chains)

It's what i use to teach rigging..  

 advanced skeleton is actually very very good.  I highly recommend it to any one looking for an autorigger. 

 check out the free rigs built with it for examples.. 

also the Malcolm rig from Anim School is a really good example, and perhaps one of the best free rigs I know out there. 

 hth

-=s

stephe...@gmail.com
http://smannimation.blogspot.com/
http://nymayausersgroup.blogspot.com/
http://smann3d.blogspot.com/

[cal...@glassworksamsterdam.nl]

Cheers Anthony, that's great to know. Thanks for taking the time to share those links. All makes a lot of sense.

Okay, interesting smann, this strikes me as the best workflow. You do flip the local rotation axis, but make sure it still behaves in a 'symetrical' fashion. I'll give it a try soon. Thanks for all the tips guys. :) much appreciated.