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Liquify with position expression

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Joey ForemanLiquify with position expression
by on Feb 1, 2011 at 4:37:12 pm

Hello all. I have pickwhipped the position property of the Distortion Mesh Offset of the Liquify tool to the position property of another layer. I can see that the offset point is following the position of the other layer just fine, however, the liquify effect itself is no longer affecting the layer it's on. I'm still on CS4.
Any suggestions?

Joey Foreman
Editor/Compositor/VFX Artist


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Joey ForemanRe: Liquify with position expression
by on Feb 1, 2011 at 6:39:57 pm

Both layers are 2d.

Joey Foreman
Editor/Compositor/VFX Artist


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Olin PadillaRe: Liquify with position expression
by on Feb 1, 2011 at 7:38:44 pm

I tried to re-create the effect, and it worked fine fore me. However, the offset was almost completely off screen, and I almost didn't notice the liquify effect. That might be what is happening to you.


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Joey ForemanRe: Liquify with position expression
by on Feb 2, 2011 at 2:59:47 am

That is indeed what's happening. The problem is that I can't seem to get it back into position.
I admit to being terrible at expressions. I was able to get it -the offset point- into the correct position horizontally by tagging on -470 after the expression,
so that it reads thus:

thisComp.layer("Tony High School.jpg 2").transform.position-470

I could see that the initial Distortion Mesh Offset point originated at the top left corner of my comp which is 720 by 480, and for no go reason really I tried a value of 480 just to see if I could get the distortion point back. I did but it was a little off horizontally so I changed it to 470 and now it's exactly where I need it - horizontally.

So for anyone with even the most rudimentary knowledge of expressions -
how to I also offset it vertically in the expression? Do I need an array? I just need it to offset about 150 pixels upward.

This just seems too basic to post to the Expressions forum.

Joey Foreman
Editor/Compositor/Expressions Novice


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Walter SoykaRe: Liquify with position expression
by on Feb 2, 2011 at 4:10:16 pm

Yup, you need an array:
[thisComp.layer("Tony High School.jpg 2").transform.position[0]-470, thisComp.layer("Tony High School.jpg 2").transform.position[1]-150]


A point expression should return two values (x and y). The expression above subtracts 470 from the referenced layer's x position and subtracts 150 from its y position, then returns those coordinates.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Joey ForemanRe: Liquify with position expression
by on Feb 2, 2011 at 7:50:09 pm

Perfect! Thank you so much, Walter.

I dabbled in expressions a few years back, then let those skills kind of fall by the wayside. I'm inspired to brush up on them again now.

I think I'll start with Chris & Trish Meyer's Deeper Modes of Expression series over at ProVideo Coalition.

Thanks again!

Joey Foreman
Editor/Compositor/VFX Artist


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Walter SoykaRe: Liquify with position expression
by on Feb 2, 2011 at 10:07:34 pm

Happy to help, Joey.

Instead of hard-coding values like the 470 and 150 into an expression, I usually pickwhip to an Expression Control [link] effect. For this, you could either use two slider controls (one for X, one for Y) or a single point control.

A couple big advantages to using expression controls:
  • They're easier to get to than hard-to-find, hard-coded numbers in a large block of code
  • They're reusable (in case you need to use the same value in a couple different places in the code)
  • You can scrub them interactively
  • You can animate them (with either keyframes or additional expressions)


Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Joey ForemanRe: Liquify with position expression
by on Feb 2, 2011 at 10:28:36 pm

Even better :)

Joey Foreman
Editor/Compositor/VFX Artist


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