• Adobe After Effects Expressions

  I need and expression to sync the range of a slider control with the position of a solid

  Posted by Tommy Dimmel on January 16, 2015 at 9:50 pm

  Hi Friends!

  I need an expression that will sync the ranges of two different animations in sync with one another. The animation consists of a man’s head that vomits rainbow sludge. I want to link up the range of his jaw opening and closing with a slide control that is linked to the particles/sec parameter of the trapcode particular effect that creates the rainbow vomit. Additionally, the jaw animation exists in one comp (‘Comp A’) while the slider control exists in another comp (‘Comp B’). Simplified, this is what I need an expression for:

  1. Y position of jaw in Comp A: 474.5 to 611.5 and back to 474.5
  ***Sync with****
  2. Slider control in Comp B: 0 to 1000 and back to 0

  Here’s a video of it, displaying what I’ve achieved so far without the expression:

  https://www.youtube.com/watch?v=5QosGXbsol4

  Since I will be having to animate them puking quite a few more times, it will save me time to have an expression, so I only need to create keyframes for one parameter.

  Thank you!

  Tommy Dimmel replied 11 years, 4 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Dan Ebberts

  January 16, 2015 at 10:30 pm

  It’s hard to compose an exact expression without knowing the layer names or which parameter is driving the other, but it’s probably a job for linear(), which can be used to convert one range to another, like:

  linear(drivingValue,474.5,611.5,0,1000)

  or,

  linear(drivingValue,0,1000,474.5,611.5)

  It gets more complicated if there is a time differential between the comps (e.g. one comp is nested in the other and doesn’t start at time = 0).

  Dan
• 

  Tommy Dimmel

  January 17, 2015 at 9:08 am

  Thank you so much for responding to me!

  Here’s the exact details I left out on my first post

  Name of the main comp: “Heads”
  Parameter to control: the position of the jaw on the head
  Range of that control (on the y axis): 474.5 to 611.5 ***
  ***This control is to be the driver for the following parameter

  Name of comp, which is nested in the above comp: “Head 3 Barf”
  Parameter to control: A slider control
  Range of that control: 0 to 1000

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