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View Full Version : Need a bit of help for 3-joint-IK-setup

whizz
08-09-2005, 03:05 PM
hey folks,

so i am trying to set up an IK spider leg with 3 joints.

http://www.maerlyn.de/cgtalk/normal.jpg

but i do encounter a bit of a hassle: when i move the ik-handle to the base to bend the leg, i get some uncontrollable rotation of the first bone (the one at the base)

what i want to do, is to create a controller which enables me to control this kind of rotation as well, so that i can bend the leg and decide on the look of the bend like on the pictures (done with fk)

bend01:

http://www.maerlyn.de/cgtalk/bent01.jpg

bend02:

http://www.maerlyn.de/cgtalk/bent02.jpg


maybe someone can point me in the right direction, so that i can find a solution (pole vector orientation didn`t help on that problem)

cheers
patrick
el-vio
08-10-2005, 09:24 AM
hi ,

you should try to put 2 or 3 Ik chain, each beetween 2 joints, and after set parent or constraint or/and connect it with some locator and attributes.

bye
alec.tron
08-16-2005, 09:42 AM
Hellooo,
you re having a problem here that s annoying me for a while now as well. Which is that you can t control the rotation of an IK root joint.... there s only a workaround which lets you reach the rotations you want which is what el-vio allready said.
You will need 2 (2 joint) IKs in that chain, one from joint 2-4 and one from 3-5, now you can key both IK handles to reach your positions....but it s not ideal as you ll mostly counteranimate....
Another way would be to play around with joint stiffness until you reach a solution that comes close to a behaviour you want....but you ll never be able to control the root IK joint with that either....
just my 2 cents...
and if you come across a way to control the root Joint in an IK let me know... ;)
c.
whizz
08-18-2005, 11:53 AM
i finished the rig somewhere last week. it's quite ok, but there is this missing part which i presented here. so this rig is in my opinion only 80% controllable of what i would wish for

anyway ... did some animation and compositing after work ... still doing some tests on the textures

click here (http://www.uni-weimar.de/%7Ejunghan3/public/03finalComp.mov)

maybe i'll find it out some day ... it must be possible ... wich i could have a look at the rigs of "8 legged freaks" ;)

cheers
bahman
08-20-2005, 12:14 AM
There is a controler in joint Attr that called "stiffness".

If u change to positive value (in X, Y & z) your joint will rotate more stiffer while you r moving IK.

In this case maybe u should change it to negative value I

I hope this can help u.
bunkle
08-23-2005, 12:32 AM
what you want to do is first place an ik handle from the third joint to the last joint, then place an ik handle from the second joint the the last joint. create a controler and snap it to the end joint and parent the ik handles to it. now create an object for a pole vector and place it above the highest joint and a good distance out past the last joint, now place a polvector from it to both ik handles. the ik settings are autopriority off, solve enable on, snap enable off, sticky on and leave priority, weight and poweight at one, that should give you the results that you are looking for.
whizz
08-23-2005, 09:19 AM
i just tried it out and it works already pretty nice ... need to finetune it a bit now

thanks bunkle!!! thanks guys!!!

:)
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