• Adobe After Effects Expressions

  How do I do a complex if/else structure?

  Posted by Erin Shelby on November 8, 2007 at 1:28 am

  Hi All,

  I have a slider and basically will be using only values 1-4 on it…

  I have a series of solids underneath it that I want to change opacity depending on what value the slider is at, so:

  solid 1
  if slider is 1
  then opacity 10
  if slider is 2
  then opacity 25
  if slider is 3
  then opacity 50
  if slider is 4
  then opacity 100

  etc etc. Solid 2 is different and solid 3 is different. I was just wondering if there was a way to structure this that is better then a complex nestled if/else strucutre…thoughts?

  -Erin

  Mike Clasby replied 18 years, 6 months ago 4 Members · 4 Replies
• 4 Replies

• 

  Dan Ebberts

  November 8, 2007 at 1:39 am

  Maybe like this:

  idx = Math.round(effect(“Slider Control”)(“Slider”));
  myArray = [10,25,50,100];
  myArray[clamp(idx,0,myArray.length-1)]

  Dan
• 

  Colin Braley

  November 8, 2007 at 1:51 am

  There is no super simple way to do something like this. Some people like to use something called a “switch statement” in situations like this. For instance, the psuedocode you wrote in in you post would look like this written as a switch statement:

  
switch ( slider ){
case 1:
10
case 2:
25
case 3:
50
case 4:
100
default:
100//if the slider wasn't 1 ,2, 3, or 4
}


  Im not sure if this is the exact syntax you would use for a switch statement in javascipt, and i actully don’t even know if there is a switch constuct in javascript….however, most modern programming languages do have a switch construct.

  Personally, I would never use a swich statement, I prefer just using if statements….I feel that while code using switch statements might be more concise it is more-error prone because people don’t use them as often. Also, there are a bunch of other issues that crop up when you forget to use the “break” keyword peoperly within a switch statement, but I dont think I’ll elaborate on that one…

  Anyway, if you REALLY want to use switch statements, check out wikipedia and read about them…

  https://en.wikipedia.org/wiki/Switch_statement

  ~Colin

  http://www.colinbraley.com
• 

  Erin Shelby

  November 8, 2007 at 1:56 am

  Thanks Dan/Colin! I’ll give it a whirl.

  -Erin
• 

  Mike Clasby

  November 8, 2007 at 9:11 pm

  I can’t getColin’s to work, love Dan’s.

  Here is an old style if/else, it needs hold keyframes:

  First you need a Null named “control”. Add a Slider to the Null. Add this expression to Opacity:

  n = thisComp.layer(“Null 1”).effect(“Slider Control”)(“Slider”);
  if (n==1) {
  10
  } else if (n==2) {
  25
  } else if (n==3) {
  50
  } else if (n==4) {
  100
  } else {
  0
  }

Reply to this Discussion! Login or Sign Up