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mirrored expressions values?

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Kevin Olmsted
mirrored expressions values?
on Aug 2, 2007 at 2:47:26 am

I am a comfortable After Effects user just getting into expressions so I don't know a lot of the scripting yet. Here's my problem...

I am compositing fairy wings onto an actress for a friend's short film. I tracked the tracking points, attached the track data to a null object, and attached the wings to the null object using a simple pickwhip.

The first effects test looks amazing for 30 minutes of work. I added a small wiggle expression on the Y rotation to each wing to give the look of small flutters. But they move independently of one another all willy-nilly.

Is there an expression I can write so one wing mirrors the other wings movement? If righty swings out, lefty swings out the other way the same value... you get the picture. I tried pickwhiping one Y rotation to the other and I think I'm on the right track but don't know where to go from there.

Any help would be greatly appreciated.

Also can anyone recommend a good book on learning expressions? All I've got is my AE manual.

Thanks mucho...


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Dan Ebberts
Re: mirrored expressions values?
on Aug 2, 2007 at 3:33:35 am

You should just be able to pickwhip one rotation value to the other and put a minus sign in front. Depending on how you set the wings up initially, you may also have to add 180 degrees or 90 degrees (or minus 90 degrees) to get it right. Something like this:

-thisComp.layer("left wing").transform.rotation + 180;

Dan


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Lord Scales
Re: mirrored expressions values?
on Aug 3, 2007 at 2:25:15 am

[Kevin Olmsted] "Also can anyone recommend a good book on learning expressions? All I've got is my AE manual."

These 2 sites are really good online references for expressions:
http://www.motionscript.com (Dan's site)
http://jjgifford.com/expressions/

Well, http://www.wikipedia.org is useful especially if you want to look for some mathematical function that is used somewhere without too much explanation.

Don't try learning all in a single day, be patient and you get there!


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Kevin Olmsted
Re: mirrored expressions values?
on Aug 3, 2007 at 11:31:28 am

Thanks guys, for the help and the recommendations!

The advice you gave worked perfectly (I needed to add the 180 to my expression.

I will be heading to the links shortly! Again, thanks!

I learn something new in AE every day.

Kevin


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