• Adobe After Effects Expressions

  Sequentially Animating Masks Using mask(index)

  Posted by Mike Kirsch on January 26, 2015 at 9:25 pm

  I’m trying to sequentially animate a series of masks to reveal parts of an image. The expression is on the expansion property of the first of 8 masks, and is based on a slider value and was inspired by a tutorial at Tuts+ (https://cgi.tutsplus.com/tutorials/how-to-create-infographics-that-animate-themselves–ae-26627)

  According to: https://helpx.adobe.com/after-effects/using/expression-language-reference.html — mask(index) has a return type of Mask, (which isn’t a number) so AE keeps giving me errors on the expression. I am trying to return a number so that I can create a sequential delay based on the index number of each mask.

  Any ideas? Thanks in advance.

  m = thisComp.layer("Null 1").effect("Slider Control")("Slider");
delay = m+mask(index);
exp = thisComp.layer("Null 1").effect("Slider Control")("Slider").valueAtTime(delay);
exp

  Mike Kirsch replied 11 years, 5 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Dan Ebberts

  January 26, 2015 at 10:26 pm

  For an expression on the Mask Expansion property, this should give you the index of the mask itself:

  thisProperty.propertyGroup(1).propertyIndex

  dan
• 

  Mike Kirsch

  January 27, 2015 at 7:24 pm

  That did the trick. Thank you so much! This was the first time I’ve ever used an expression that wasn’t just straight copy/pasted, so thank you! (Although it was mostly stolen from a tutorial, but still – you have to learn somehow.)

  I also caught some other errors as I refined the expression. My final code is below.

  delay = thisComp.layer("Null 1").effect("Delay")("Slider")
d = delay*thisProperty.propertyGroup(1).propertyIndex;
t = time-d
exp = thisComp.layer("Null 1").effect("Slider Control")("Slider").valueAtTime(t);
exp

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