Max link constraints -- how to NOT inherit previous position?

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  10 October 2012
Max link constraints -- how to NOT inherit previous position?

Hi there,

I'm a Maya guy and relatively new to Max. I've been using Link Constraints for a while now, and one major headache I've had using them: they always inherit the position+rotation of the last object that controlled it.

So the problem is that if I link a child to a parent and then adjust the parent's animation prior to the child being constrained, ALL of my animation is now based off of the parent's new animation. The big problem I face is Linking to World. I just want objects to stay in World space when they are linked to it, but they always change location based on the parent's prior anim.

Is there another constraint I should be using to isolate objects to specific parent spaces? I've had to do a lot of rework lately because I animate pose-to-pose and not straight thru. I'm familiar with Maya's parent constraints and looking for something just like that.

Thanks!
 
  10 October 2012
Link constraints do what you describe,
when you change the animation of one of the parents used before or when the constraint is on, the changes off the parents' transforms do offset the transform of the child, logic and normal but tricky when moving keys; parent-transform keys and child-constraint-keys need to be moved 'together'.

To correct the mess, just animate your character taking up the bowl (example), correct your animation and hide the bowl while animating, or duplicate one just simply parented to the hand for reference.

Once finished the animation, on the original bowl, correct in the motion-panel the frame-number of each key of your constraint, one by one, starting with the first one that is 'de-framed' and things will be getting back in order very easy.

Instead of linking to the world, you might link to another object.
Constraint keys need to be placed on a frameframe basis, on/off. Yes, you can weight the influence on several frames but the outcome can be very confusing. And this is maybe what's happening in your case sometimes.
Also, when 'reframing' constraint keys, it can happen that you destroy, write on other parent keys. Just stay calm and redo the constraints.

Hope this is clear and helps you out.
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  10 October 2012
Thanks for the explanations. If I'm understanding correctly, fixing it can be considerable amount of work to get around it, especially when there are hundreds of keyframes involved and multiple link constraints built out. I guess the best solution would be to write a script for it that plots keyframes of the target to a world space object, edit the keyframes that will offset everything, and then replot to fix the offset (if that makes sense).

At the end of the day, I'm hoping they might implement some kind of "no offset" option that anchors the object-space of each link.
 
  10 October 2012
might be...

...but all depends of you're scene,
Personnaly I don't use the Linkconstraint while animating. As it's behavior becomes unpredictable when changing timing. I use them in the scene once I'm happy with the animation.

I learned how to use the tool (and make corrections) with a simple box gives a box gives a box to another box selfmade excercise. Handy to figure out the logic of the tool.

Dominique
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  10 October 2012
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