Polevector and aimTarget...Mathematical explanation.

[ShadowM8]

Well since your aim target is directly responsible to where your lower arm will end up in space you can't parent the two, it's an obvious cycle. Whether you can trick the built in dependency check is not the point as that sort of setup is inherently wrong.

[Paquitoo]

Ok so what would the best spot to parent the aimtarget ? the shoulder ? Is there any better way to deal with this controller than translating it.

[ShadowM8]

Shoulder or chest would be where you parent it. The standard way to control the aim vector of an IK chain is really the most preferred by animators from my experience.

[Paquitoo]

Hi, I made some experiment and I found something that I'm wandering if it would be a better solution.

If you make a standard ik chain with bones, than you make a second Ik chain this time with point helper exactly at the same position and orientation as the bones. You parent your aim target to the Elbow point helper and you take the ikhandle of the bone chain and you register the aim target as polevector. And finally you parent both IKHandle to a wrist controller.

You end up it an IK aim target that follow the bone ik chain. The problem that I see is that theres no polevector on the helper IKChain so if you take the Wristcontroller and go to close to the UpperArm the chain pop, but I think it's a better solution than always to have to translate the aim target each time you move the arm. Isn't it ?

[ShadowM8]

It's not a better solution because you are introducing unpredictable results that would require significant corrections in certain poses. As I said before most animators really prefer to animate the pole vectors by translating it in place where they need it so why over engineer yourself.

However if you were to do something like this than your thinking process is correct. You'd need to devise a secondary system that will drive your pole vector independent of your IK chain. Now the trick is to make it predictible and stable in it's results.

[Paquitoo]

Thanks a lot I'll keep that in mind

[PEN]

There are ways to handle this. I have a system where the elbow target can either rotate with the arm or stay with the body. What I do is setup a look on a point helper. The helper is aligned to the shoulder and parented to the clavicle. Then have it look at the control object that the IK solver is parented to. Also use this object as the up vector. The parent the elbow target object to the point helper. To set up a blend from one to the other just have another point helper blend between the orientation of the clavicle and the look at point helper. The link the elbow control to it instead.

[Paquitoo]

Thanks Pen that's pretty helpfull I'll put that in my rig for sure

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