• Adobe After Effects Expressions

  Exponential slider query…

  Posted by Danny Parsons on May 4, 2008 at 9:28 pm

  Hi there – ‘May the fourth’ be with you all…

  I’m having some trouble figuring out how to get a slider to control an effects property in the precise way I want it to. I’d initially thought I could just use the linear() function, but clearly I hadn’t thought things through properly…

  Describing the actual scenario would probably be unnecessarily long-winded to go into, so I’ve just come up with an analogous hypothetical situation, which should help explain more simply the basic principle that eludes me…

  Let’s say that I want to link a layer’s opacity value to a null’s slider control and have it translate the input in the following way:

  When the slider is set at zero, opacity = 50
  If we turn the slider up to 1.0, opacity = (50* 1.05)
  And then if we turn it up another notch to 2.0, opacity = (50* 1.05)*1.05
  … And so on, multiplying the previous value by the same amount each time. It also needs to work in the opposite direction – if the slider is set to a negative value, it should divide the previous value by the same amount each time, so if the slider = -1.0, opacity = (50/ 1.05).

  Thanks in advance,

  DP

  Danny Parsons replied 18 years ago 2 Members · 2 Replies
• 2 Replies

• 

  Dan Ebberts

  May 4, 2008 at 11:00 pm

  Like this, I think:

  slider = effect(“Slider Control”)(“Slider”) ;
  50*Math.pow(1.05,slider)

  Dan
• 

  Danny Parsons

  May 5, 2008 at 12:12 pm

  Thanks Dan,

  That’s done the trick perfectly.

  DP

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