How do I animate an extra set of arms?

[Pokintail]

Hi, I'm currently working on an animated story based on a Hindu myth, and one of the characters is a deity named Yama. To be consistent with how Yama's traditionally portrayed in religious art, I added a second set of arms to his body, and a corresponding set of arm bones to each consisting of a Bicep, Lower Arm, and Hand.

 

Here's the problem...

 

When I try to animate the second set of arms, they flop all over the place. The original arms (I'm used the standard AM skeleton) move steadily, that is, they only hinge in one direction, and when I move one bone the rest move realistically with it. What exactly are the settings used to make them move like that, so I can apply those settings to the extra set as well? Do I need another bone, or is there some special constraint, or what?

[robcat2075]

Without knowing how or what you rigged the character with it's hard to say. I'd guess that you left some important element out of the second set of arms that was inthe first?

 

TSM 2 has options for multiple limb sets but I don't know that you used TSM2.

[Pokintail]

Without knowing how or what you rigged the character with it's hard to say. I'd guess that you left some important element out of the second set of arms that was inthe first?

 

TSM 2 has options for multiple limb sets but I don't know that you used TSM2.

 

I'm almost sure that the problem is that I left something out, but I'm not sure what. You see, I didn't create the original skeleton, I just added arms to it. The skeleton I used was "2001 Skeleton.mdl," the one included with the Animation Master program (at least, version 10.5, which is the one I'm currently using). As best I can tell, the two arms included with that skeleton feature five bones: Bicep, Forearm, Hand, Arm Steady, and Arm Hinge. The new arms feature Bicep, Forearm, Hand, and Arm Hinge, and are located beneath the original Shoulder in the heirarchy. I'm not sure exactly what Arm Steady does, as my only real resource in this is the tutorial book that comes with the package and, needless to say, it's missing a lot of key information.

 

In this post I'm including a picture excerpted from the animation (with bones visible), with the character in question Yama speaking to another character, Yudisthira. The upper arms are the ones where I added bones.

 

Just as a side note, all of Yama's body parts are two-dimensional, except for his crown and sarong (clothing). This is so as to replicate the look of a Balinese shadow puppet show, which is what the animation in its final form is designed to resemble.

[robcat2075]

As best I can tell, the two arms included with that skeleton feature five bones: Bicep, Forearm, Hand, Arm Steady, and Arm Hinge. The new arms feature Bicep, Forearm, Hand, and Arm Hinge, and are located beneath the original Shoulder in the heirarchy.

 

Rigs often have a number of hidden bones that help manuver the visible bones and then have constraints applied that make everything work together.

 

I'm not an expert on the AM2001 rig so I couldn't tell you exactly what might have been left out when you created the second set of arms.

 

I made short tut on simple IK legs here..

 

the simplest IK leg

 

Even though it's for a "leg" you could use the same tactic on an arm.

[Pokintail]

Thanks for the suggestions. I watched the IK Legs tutorial and tried applying it to Yama's arms, but when I constrained the biceps to aim at the nulls I created I found that they became locked into place. The biceps wouldn't move at all, they'd just stay frozen there, pointing towards the nulls.

 

Is there a way to copy the bones in the original arms and reassign them to the extras?

[robcat2075]

when I constrained the biceps to aim at the nulls I created I found that they became locked into place. The biceps wouldn't move at all, they'd just stay frozen there, pointing towards the nulls.

 

If you got a different result, that's a very strong indicator that you skipped a step or did a step differently, or did them in a different order. Beyond that it's impossible to diagnose this just by words. There's a hundred things you could have done differently and no way for me to know which one.

 

I would suggest removing all the bones from one arm and starting from scratch on one arm. Don't copy anything from the arms you already have. Obviously that isn't working because some important part out is getting overlooked. Without watching you there's no way to know which one is being left out.

 

here's a very simple FK arm alternative.

 

SimpleArmMP4.mov

[itsjustme]

A wild stab in the dark....when you copied the arm constraints, did you rename the bones in those constraints? If not, they would be applied to the set of bones you copied. The bones you copied would automatically be renamed, so you would either have to changed the constraints to match those names or rename them the way you want. An easy way to do the renaming is in a text editor.

 

Drag the arm bones to an empty model, drag the appropriate constraints to the empty model, save the model under whatever temporary name you want, open the new model in a text editor and do a "search and replace" on the names of everything that will be a duplicate. Then, save the model in the text editor (not as a text file), open the edited model in AM, drag the bones and constraints to the original model and set everything up the way you want it.

 

Hope that helps.

[Pokintail]

Thank you so much, RobCat2075. I watched your tutorial and did just as you advised on the Yama model and animation, and it turned out wonderfully. I'll be sure to keep it in mind working on any similar projects in the future.

 

Itsjustme, thank you as well, though RobCat's advice turned out to be simpler for this particular project. Should I ever be modeling extra-limbed characters again, though, I'll be sure to do as you suggested.

 

Again, thank you both. Hopefully the completed animation will be on the A:M Films gallery soon--it's part of a larger project being done for the Bali Street Dog Foundation in Indonesia.

[phatso]

Here's a suggestion that wouldn't work in most any other case: Why not create a second instance of the model and delete almost everything except the arms? Resize the second model so it can "live" inside the first. That way whatever rigging complexities may be in the model will still be there. You won't have to worry about losing them when you transfer.

 

Admittedly, this is the "wrong" way to solve the problem. It's a quick and dirty workaround and you wouldn't use it if you were building a model you were going to use again and again. But given the stylized form and movements here, it might be a quick shortcut that will get you through this project.