Adobe After Effects Forum
Position null to Scale Y only, fishing hook
Position null to Scale Y only, fishing hook
by Hunter Hempen on Nov 13, 2019 at 3:48:30 pm

Here's the set up - I have a fishing hook on the end of a spiraling line that coils. Ideally, I'd have the line bounce down by animating the Y scale only on a null at the top of the line, to kind of squish the fishing line coils and give that illusion, but have the hook remain the same scale on the other end of the line as it jiggles around via manual keyframing on rotation.

I have tried this one from you, Dan, on the scale for the hook:

value*(100/thisComp.layer("Hook Null").scale[0])

But the issue seems to be it obviously only works if all three scale directions are linked. I tried switching the [0] to [0,0,0] but the hook still scales down. I am simply ignorant on the expression lingo. However I'm wondering if I need an extra null attached at the end of the line maybe? So visualize this:

Null Line Top
---
Coiled Line
---
Null Line Bottom
---
Hook

Not sure if that's necessary but I think the expression from earlier is the answer just need to format it correctly.

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Too bad she won't live! But then again, who does?
-Gaff
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Re: Position null to Scale Y only, fishing hook
by Cassius Marques on Nov 13, 2019 at 5:34:39 pm

if you don't want something to scale, forget about scalling...use the bottom null's position for the link.

Instead of parenting and compensating (as I understood you're trying), link the hook's position with an expression:

a=thisComp.layer("Null Line Bottom");
a.toComp(a.anchorPoint)


Cassius Marques
www.zapfilmes.com


Re: Position null to Scale Y only, fishing hook
by Hunter Hempen on Nov 13, 2019 at 7:26:35 pm

Hey Cassius,

This works great, let for I'm working with 3D layers and for some reason that expression adds about 668 arbitrary pixels to my z-depth, so when I scale with the top null, there's some distance offset that's slipping. Everything is nulled to each other like in my hierarchy example, and all the layers are at same z distance to start, so not sure why that would be happening?

I slipped it back with my little math trick, but even at the exact same z-depth from an above camera view, when I adjust the scale of the top line null, the hooks slips from the bottom line null position, even though it's correct.

a=thisComp.layer("Bottom Line Null");
a.toComp(a.anchorPoint)+[25,-85,-668]

-----
Too bad she won't live! But then again, who does?
-Gaff
-----


Re: Position null to Scale Y only, fishing hook
by Cassius Marques on Nov 13, 2019 at 7:57:51 pm

I disregarded the 3d part, my bad. Maybe instead of toComp, use toWorld ?

This layer space transformations don't come naturally to me. It usually trial and error until I get it working.

Cassius Marques
www.zapfilmes.com


Re: Position null to Scale Y only, fishing hook
by Hunter Hempen on Nov 13, 2019 at 11:22:32 pm

Sorry didn't respond earlier, was working through end of the day. That worked! Just that one simple toWorld and a little math adjustment. Thanks so much!

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Too bad she won't live! But then again, who does?
-Gaff
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