Arm Rigging: TroubleShooting

# 1 10-12-2006 , 09:31 PM

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Hi all, I am trying to rig some arms along with IK Handles but I stumbled a roadblock and can't figure out why my arms are not bending right........here's a picture to show what I mean..

....Basicly, after smooth binding and adding an IK Handle then trying to bend my arm it bends the wrong way.

Any tips on how to fix this?

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# 2 11-12-2006 , 02:02 AM

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i believe the way your ik handle rotates is based upon the slight amount of bend you put into your joints before you skin... make sure you have a slight bend the way you want your elbow to bend before you skin and when you create the ik handle you should be ok.

Accept no substitutions.

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# 3 11-12-2006 , 05:09 AM

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As NeoStrider said, you need a bend in your geometry at the elbow to get it to bend properly. Your arm looks like it is modeled straight, so I'm assuming your bones are straight, as well. Add a slight bend at the elbow, and you should be fine. Also, you can add a constraint control to the elbow so it bends more naturally. That way, you can move the arm, and have better control over where your elbow is pointing.

Eric Tacti
3D Artist

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# 4 11-12-2006 , 06:00 AM

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Hello NeoStrider / erictacti,

What confuses me is that I did bend the elbow a bit and after adding the IK Handle it bends the opposite..like depicted in that picture I posted above.......

erictacti: Where can I find a tutorial on adding constraint controls? Or would you mind guiding me on this?

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# 5 11-12-2006 , 07:38 AM

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Sure, I will try to guide you.

Basically, what you're going to want to do is create some type of control. Can be anything. I usually use a locator, control box, or a custom nurbs curve shape.

Anyway, position the control behind the elbow while in it's default pose.

With the control still selected, select that arm's IK Handle. Within the Animation Toolbar, select:

Constrain -> Pole Vector Options Box

In the Options Box, you probably won't have to adjust the weight very much. In this case, since it looks to be a human arm, try something between 0.05 and 0.1, which is a safe bet.

Then, it is basically done. If you have a bend in the arm, and the control is properly placed, the elbow should move up and down with the control. The IK Handle can still be used to move the arm around in any fashion, but the elbow will stay pointed at it's control. This way, you can move the arm around, and position the elbow manually.

I hope this helps!

Eric Tacti
3D Artist

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# 6 11-12-2006 , 08:20 AM

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Originally posted by erictacti
Sure, I will try to guide you.

Basically, what you're going to want to do is create some type of control. Can be anything. I usually use a locator, control box, or a custom nurbs curve shape.

Anyway, position the control behind the elbow while in it's default pose.

With the control still selected, select that arm's IK Handle. Within the Animation Toolbar, select:

Constrain -> Pole Vector Options Box

In the Options Box, you probably won't have to adjust the weight very much. In this case, since it looks to be a human arm, try something between 0.05 and 0.1, which is a safe bet.

Then, it is basically done. If you have a bend in the arm, and the control is properly placed, the elbow should move up and down with the control. The IK Handle can still be used to move the arm around in any fashion, but the elbow will stay pointed at it's control. This way, you can move the arm around, and position the elbow manually.

I hope this helps!

Originally Posted by

Here it is, I used a locator and I guess I did it right? As you can see in the pic my arm still bends wrong and can't to seem to figure out why....though I bended elbow slightly it still bends the opposite side......

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# 7 11-12-2006 , 10:47 AM

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PROBLEM SOLVED

As I continued invesitgating why it bends wrong I decided to try something that I thought might be the problem.....because my arm model consists of two meshes I thought maybe the elbow joint my be too close between both upperl/lower meshes so what I did is move vertices higher on the upper mesh. Well, seems that did fix the problem....here's a picture to show what I mean..

EDIT: Another helpful thing is too bend the arm skeleton at the elbow, regardless whether the arm mesh is straigt.

Last edited by Gus; 11-12-2006 at 07:14 PM.

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# 8 12-12-2006 , 12:26 AM

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Yeah, the arm bones definitely have to have a bend in them, regardless of whether the arm geometry does. It just makes for better deformation when the geometry does, too. That was mentioned earlier. Judging from that pic, though, the elbow bend now seems to be too high on the arm, unless you were going to add more to that sleeve.

But, I'm glad it worked out for you!

Eric Tacti
3D Artist

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# 9 12-12-2006 , 06:25 AM

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Originally posted by erictacti
Yeah, the arm bones definitely have to have a bend in them, regardless of whether the arm geometry does. It just makes for better deformation when the geometry does, too. That was mentioned earlier. Judging from that pic, though, the elbow bend now seems to be too high on the arm, unless you were going to add more to that sleeve.

But, I'm glad it worked out for you!

Originally Posted by

I am still learning this stuff and am really want to thank you and all of you for helping on this.

P.S. Maya is quite cool! user added image

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# 10 12-12-2006 , 06:42 AM

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No problem. We all had to start somewhere!

And yes, Maya is a great tool. Keep working at it, and you will see just how awesome your creations become!

Eric Tacti
3D Artist

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# 11 13-12-2006 , 08:02 AM

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Originally posted by erictacti
No problem. We all had to start somewhere!

And yes, Maya is a great tool. Keep working at it, and you will see just how awesome your creations become!

Originally Posted by

Sure thing! Hey I am still trying to tweak/adjust the hands/fingers and I need to rotate the pivots on the fingers so they align correctly and bend right, but am not sure how to do that. I can move the manipulator/pivot by pressing INSERT on the keyboard.

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Arm Rigging: TroubleShooting

PROBLEM SOLVED

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