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Dynamic "double" chain rig?


heyvern

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I am just doing this for fun... but...

 

Anyway...

 

Here is an animated GIF that describes what I am trying to achieve.

[attachmentid=10423]

 

How would you go about getting that type of constraint at the base?

 

I admit the illustration is "incorrect". One side would be "shorter" than the other and cause a slight "tightening" of the chain due to the difference in distance from the top to the connection at the base.

 

I tried using a shorter chain of bones between the two chains and used a kinematic constraint of the last bone of each chain to the last bone of this center chain.

 

It sort of worked... but not quite. If I offset any type of constraint the base of the chains become "disconnected". If I orient like... the rotations of the bones on the chain on the opposite side just mirrors the other side and becomes disconnected.

 

The problem is... each chain has to work independently... but still be fixed to the same point.

 

Ultimately I would like to use a dynamic constraint so this thing can "swing" when moved.

 

Any brainiacs willing to clue in a constraint challenged fat guy?

 

I failed math... keep that in mind... I didn't fail math exactly... I just never excelled at it and have since used those brain cells to store Lost in Space reruns.

 

Vernon "Constraint Challenged Fat Guy" Zehr

double_chain_rig.gif

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Okay...

 

Will's suggestion... almost worked. Once again the problem is the base of the two chains comes "disconnected" at extremes... or even not at extremes... the last bone in the chain kind of comes off.

 

Colin... uh... can you explain that illustration? It looks like you have the bone chains in two different directions?

 

Wouldn't you need both chains "hanging down"? The big bone at the bottom would be the kinemtic target for both chains? Or is it a part of the chain?

 

Or are there two big bones there... with one a part of the chain and the other one the target...

 

--------

 

Maybe just one long chain that hangs down in a loop. If I put dynamics on that... but then the gizmo at the bottom... how do you keep the chain "around" it?

 

That is why I went with two separate chains.

 

---------------

 

...remember I failed math... I also failed english and french... okay I didn't fail... but I am using those brain cells for Starsky and Hutch reruns.

 

Vernon "!" Zehr

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Okay...

 

This has the the two chains with the last bone of each targeted to the last bone of a middle chain that has a dynamic constraint... otherwise I don't get any dynamic swinging.

 

Unfortunately... this doesn't work because the chains on either side are obviously "held up" by the middle chain so they don't get "taught" at the end of the swing.

 

This would work perfectly with one chain... I just can't get my head around how to do it with two chains.

 

It could be that this can't be done with dynamics... since you have two independent "forces" (the two chains) each having an effect on the dynamics of the swing... as it goes up... one side is pulling down on it... visa versa...

 

I will keep fooling around.

 

[attachmentid=10430]

 

Vernon "!" Zehr

chain_hook2.mov

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Well I think I am almost there.

 

[attachmentid=10437]

 

[attachmentid=10436]

 

I ended up with 3 identical dynamic chains.

 

2 for the actual chain meshes and one in the middle for the hook/wheel thingy and to hold the null for the dynamic targets of the outer chains.

 

I used a null constrained to the last bone of the middle chain and two unparented bones lined up at the end of the outer chains... but not part of that hierarchy.

 

The null is translate only so it doesn't rotate but maintains the same distance between them. This causes the two end bones of the outer chains to "swivel" correctly as the wheel rotates. The two chains are actually suppose to be connected in a loop under the wheel.

 

This works pretty good... I have to still figure out a few things. I want to have an additional "loop" of chain under the wheel which swivels with the null and chain ends... still can't get that in my head... but...

 

... I got this far... I will persevere.

 

Vernon "!" Zehr

chain_hook3.mov

chain_rig.gif

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