CGTalk - robot arm problem

Starrider

04-15-2008, 11:37 AM

hey there!
i'm rigging a robot arm and i got some problems. if you check the attached screenshot you'll see my problem. i want to have an arm which has 2-axis-fixed rotations at each hinge.
the main problem is the change of axis at the 4th joint. if i switch the degrees of freedom off (xy or yz) the joints do what they should but the 4th joint is not solved... the same happens if i do a rotation limit.
any ideas how to solve this?
is it possible to solve this with an ik-setup? or do i have to you fk?
cheers!

ferdo

04-19-2008, 11:15 PM

this can be done easily, but not with the standard rotate-plane-ik-solver
you have to use the so called multichainsolver for things like this ...

type "ikMCsolver" and change the ik-solver on the ik-handle to that one
this should produce the results you want ;-)

cheers, ferdo

ferdo

04-19-2008, 11:16 PM

sorry, you have to type:
createNode ikMCsolver;

Starrider

04-20-2008, 07:29 AM

Thanks for your reply!
I tried that but the result seemed to be kind of instable and unpredictable. The solution I'm using now is a splitted ik-chain. So it's always one chain for xRot -> zRot -> zRot ... By parenting the ik-handles I got a pretty good result.
Cheers!

ferdo

04-20-2008, 10:19 AM

well, you are right, this solver produces a complete different solution than the rotate-plane-solver. because it is able to "break" the chain, you would also have to limit the rotate channels for this solver to work like you would expect it.

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04-20-2008, 10:19 AM

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