View Full Version : Joint Scale Constraint Problem

03 March 2011, 12:27 PM
Hi, all!

I've been having this trouble for quite some time now and it's very annoying.

I'm creating a leg with stretchiness and an ikfk-switch. I've created 3 joint chains; one IK, one FK and one Bound (bn).

I've orient constrained the bound joints to their corresponding joints on the FK and IK chains. I have an attribute ("ikfkBlend") on a control object that goes from 0-10. This attribute I have keyed with the orient constraints for the bound joints, so that 0 = IK and 10 = FK.

I made the IK chain stretchy using distance locators and this expression:


// Stretchy Limb

if (dist_leg0Shape1.distance >= 11.180) { = dist_leg0Shape1.distance / 11.180; = dist_leg0Shape1.distance / 11.180;

}else{ = 1; = 1;


And I think it's around here the trouble starts.

I scale constrain the Bound joints to the IK joints. And I key that constrain from 100% influence to 0% influence with the ikfkBlend attribute. So that, when in FK mode, the joints should not be stretchy.

When I pull the IK joints downward, so that the IK joints stretch, the Bound joints follow along nicely. But when I move the IK joints in other axis (so it's not straight down) the Bound Joints scale more than my IK joints. That makes them stretch beyond my foot control.

And that is my problem. Why don't my scale constrained Bound joints keep the same scale as my IK joints, to which they are constrained? Sometimes they scale more than my IK joints even when I'm pulling the controller straight down.

I feel like I've created this setup a million times now with the same problem. I'd really appreciate som help. It would be nice to know what I'm doing wrong here, also if you have a completely different approach to achieve what I'm attempting to get out of these legs it would be nice to hear.

I wanted to load up my scene file somewhere, so that people could check it out and see the problem more easily, but I don't know where to do that. So I hope this description will be clear enough.



03 March 2011, 09:39 AM
actualy i think is better for you to blend the deformation between ik fk and bn. so you wont use orient constraint . also i suggest you to make the stretch with the translate not with scale . anyway if you upload your scene file on mediafire or megaupload . any file hosting is ok . i will check it

03 March 2011, 07:36 PM
Thanks for the answer! Here's the mediafire-link to my scene. Didn't know about it. Great stuff, if it works :)

The ikfkBlend-attribute is on the swirly controller by the ankle, that follows the bound joints.


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03 March 2011, 07:36 PM
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