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PickWhip Expression doesn't follow parent

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Carolyne Anthony
PickWhip Expression doesn't follow parent
on Mar 30, 2017 at 2:18:38 pm

Hi I'm new,

I dragged a pick whip from one shape layer property to another (scale). I now have one box following the scale properties of another box (great!) but they scale in different directions... I tried aligning their anchor points which mostly works, but this is odd to me because the when I make a parent/child relationship with overall layers, they follow the position and scale of the parent's anchor point, regardless of where the child's anchor point is.

I tried to make a pick whip expression of the child object following the parent's anchor point to see if this would work as a quick fix, but now it flies off the screen.

Any advice appreciated.


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Daniel Waldron
Re: PickWhip Expression doesn't follow parent
on Mar 30, 2017 at 2:43:27 pm

There are multiple anchor points on a shape layer. Did you align the anchor point of the overall shape layer, or of the individual shape in the contents of you layer?


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Carolyne Anthony
Re: PickWhip Expression doesn't follow parent
on Mar 30, 2017 at 3:05:54 pm

I did both to see what would work. Aligning the anchor points of the individual shape layer helped them scale in the same direction, I was just confused why I would have to do this in the first place? Shouldn't a child automatically scale toward the parent's anchor point?


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Dave LaRonde
Re: PickWhip Expression doesn't follow parent
on Mar 30, 2017 at 3:29:55 pm

Nope -- it will scale around its own anchor point. And rotate around it, too if you animate its rotation and not the parent's.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Carolyne Anthony
Re: PickWhip Expression doesn't follow parent
on Mar 30, 2017 at 3:47:35 pm

Huh. Okay thanks guys for helping me out!


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Kevin Camp
Re: PickWhip Expression doesn't follow parent
on Mar 30, 2017 at 4:30:37 pm

you're not actually parenting, you are simply linking the property of one layer to the property of another layer with an expression. in this case you are linking the scale property, and scale is relative to the individual layer's anchor point.

as Daniel points out, shape layers complicate thing a bit, since they have multiple scale and anchor point properties and also a size property that is much like scale... you can even have multiple shape on the same layer. all of this makes it hard to trouble shoot what is happening in your comp.

in your original post, you mentioned that you were using shape layers so you could keep the stroke thickness the same when you scaled the layer. you could do that with an expression on a solid if that makes the rest of your set up easier....

example:
  • add a new solid, make it 500x500.
  • double click the mask tool to add a mask that is the same size as the solid
  • add the stroke effect and set the bush size to 10
  • option-click or alt-click the brush size property and copy/paste this into the expression field: value * 100 / scale[0]

now if you scale the solid, the stroke will remain constant. one caveat is if the scale is zero, it will kick up an error since you can't divide a number by zero.

on other potential issue, the expression only looks at the x-scale, so if you are scaling x and y separately, it may not work for you....

Kevin Camp
Art Director
KCPQ, KZJO & KRCW


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Carolyne Anthony
Re: PickWhip Expression doesn't follow parent
on Mar 30, 2017 at 9:52:15 pm

Hey thanks,

I can get a stroke to remain constant, the problem is when I have many of these solids and i'm making a parent for them to follow.


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