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Old 30-04-2005, 08:03 PM   #1
Eelco
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Question HELP !?! Parent constrain doesn't maintain offset.

I can't get this parent constraint working on my character. It needs to pick up something from the floor. So I select the character's hand, then the object and apply a Constrain > parent (I reset the options first).
But every time I apply the constrain, the object moves from its position. It looks like it tries to align itself to the new parent, the hand.
Maintain Offset is checked. What am I doing wrong here ?!?

I just stumbled onto this problem while finnishing up my animation for the march/april challange. Crap!!
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Old 01-05-2005, 10:07 AM   #2
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I didnīt use those commands yet, but what would happen if you parent the hand to the object? or if this is bullcrap - maybe move the hand that near to the object bevor parenting, so the object itself does not move..?
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Old 01-05-2005, 11:53 AM   #3
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your grouping might be off. you probably have the nad's tranlations not reset and nested in some groups or under some joints.. so when you parint cosntrain the ball thinks it is maintaining the offset. I couldn't say for sure though as its a complex problem.

but try makeing 2 cubes just in the world space and parint constrain one to the other to make sure the offset really is working properly.
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Old 01-05-2005, 06:28 PM   #4
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Quote:
Originally posted by Pony
your grouping might be off. you probably have the nad's tranlations not reset and nested in some groups or under some joints..
what is a "nad"? Or am I just missing too much sleep due to the challenge.
The hand is parented and grouped to joints and geometry. It might be that there is somthing somewhere in those couple of hundred nodes that causes all of this? hehehe.

I temporary found a workaround for it .... cut to the next scene. I just didn't have enough time to get it done properly for the march/april challenge. Have a look at my post under the newbies final theard.
I'll be out for a couple of days (celibrate my baby girl's 2nd birthday), but I will get back at this when Ive returned.
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Old 02-05-2005, 01:50 AM   #5
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if i were u id select the object first then the hand and parent
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Old 02-05-2005, 01:51 AM   #6
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as in parent i dont mean constraint. i mean hit 'p' on ur keyboard or go to edit - parent
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Old 03-05-2005, 04:50 PM   #7
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That's what I end up doing. Just parent a copy of the object to the hand and hide one when the other is visible, and cut to the next scene just before it picks up stuff during post production. It's a work around somthing that should be no problem at all. I really had planned to have the character show how it gracefully picks up things (zoomed in and even in slowmo).

I'll break down the model till I found the problem-node Pony mentioned about.
Still not sure what the "nad's tranlations not reset" is about though. Pony?
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Old 03-05-2005, 10:36 PM   #8
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LOL sorry yeah node's not nad.
(trots off embarased)

probably would be a help to see the hypergraph of the character unless you got it worked out now. There are so many ways to put them togather.

but from the animation I sean, looks good though.

Last edited by Pony : 03-05-2005 at 10:38 PM.
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Old 05-05-2005, 11:23 AM   #9
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I parent constrain the pencil (see anim. in next post) to the red hand-pad subdiv mesh, which results in the unwanted offset (the pad has frozen transformations and a deleted history). But found out that when I constrain the object to the parent mesh (R_HandWrist) or parent-parent joint (R_Joint_Wrist) of the pad mesh (R_HandPad), it works. I parented the pad straight to the joint and also works ok.


Since the constrain works on its parent's mesh, and works on its parent's parent joint, and works on the pad parented under the joint,... could it be that a mesh can not be a parent constrain target when it's under another non-joint node in a joint hierarchy or something?? (just guessing)

There must be some logic behind this. I'm determined to find out. It's gonna bug me till I figured out why (these things can keep me awake all night). ..... or is it a bug?

I learned parent constraining from the Maya 6 tutorial: Learning Resources > Tutorials > Animation > Lesson 5 Inverse Kinematics > Applying parent constraints on an IK system (link might not work).
Here the parent constrain target objects for the CargoBox are the ArmControl (parented under another mesh) and Platform (root node). Neither parented in a joint hierarchy.

Attached a hypergraph screencap of a stipped hierarchy.
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Last edited by Eelco : 05-05-2005 at 11:27 AM.
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Old 05-05-2005, 11:29 AM   #10
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The anim of the offset when I parent constrain the pencil to the handpad.
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