• Adobe After Effects Expressions

  Passing a function as an argument to another function issue

  Posted by Anton Kosarchyn on September 3, 2015 at 1:58 pm

  Hi, guys! I’ve an issue with passing a function as an argument to my own custom function. Appears error message with text: ‘Error at line 6. Function property .speedAtTime() cannot work with this class’ though the code below works just perfect outside of the function body. Please, help! Thanks!

  function eventTime (property){
var frame = timeToFrames(time);
var controller = true;
while (controller){
var t = framesToTime(frame);
var s = Math.floor(property(t));
var prevs = Math.floor(property(framesToTime(frame-1)));
if(frame==0){
break;
};
if(prevs!=s){
if(s==0){
controller=false;
};
};
--frame;
};
if(!controller){
t;
}else{
t=null;
};
return t;
};
eventTime(thisComp.layer("card 2").position.speedAtTime);

  Anton Kosarchyn replied 10 years, 12 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Xavier Gomez

  September 3, 2015 at 9:28 pm

  I don’t think you can pss this kind of methods as argument to a function.
  But passing the actual property (in your example : thisComp.layer(“card 2”).position), not a method, and then using

  var s = Math.floor(property.speedAtTime(t));
  var prevs = Math.floor(property.speedAtTime(framesToTime(frame-1)));

  in the function body, will probably work (didnt check).

  If you want to keep the possibility to use the same function for values (not speed), you could do:
  (i didnt try to undertand the code so i dont know if it’s relevant):

  function eventTime (property, isSpeed){
var frame = timeToFrames(time);
var controller = true;
var meth = isSpeed ? "speedAtTime" : "valueAtTime";
while (controller){
var t = framesToTime(frame);
var s = Math.floor(property[meth](t));
var prevs = Math.floor(property[meth](framesToTime(frame-1)));
if(frame==0){
break;
};
if(prevs!=s){
if(s==0){
controller=false;
};
};
--frame;
};
if(!controller){
t;
}else{
t=null;
};
return t;
};
eventTime(thisComp.layer("card 2").position, true);

  Xavier.
• 

  Anton Kosarchyn

  September 7, 2015 at 11:18 am

  Thanks for the reply! Your solution works great but I expanded it a bit with switch conditions, so now you can pass up to 3 properties (speed, velocity, value). So the extended code are below if anyone needs it:)
  Thanks again!)

  /*
Function can obtain time when some action happens (eg time when object speed was 0 etc.) It's based on algorithm of Dan Ebberts expression. You can pass 4 arguments:

  1. property - eg layer.transform.position etc;

  2. method - string value. eg 'speed', 'velocity', 'value'. Buy default function will obtain 'value';

  3. axis of property - you can pass 0(x-axis) or 1(y-axis) for methods 'velocity' and 'value'. For the 'speed' method it doesn't matter, but you still should pass something(0 or 1)or function will return error;

  4. triggerValue - numeric value, which triggers the function.

  For example, you want someLayer to fade out in half of a second when layer's position will be 600px at y-axis:
  eventT = eventTime (thisComp.layer("someLayer").position, 'value', 1, 600);
  thisComp.layer("someLayer").opacity = easeOut(time,eventT,eventT+0.5,100,0);
  */

  function eventTime (property, method, axis, triggerValue){
switch(method){
case "speed":
method = "speedAtTime";
var isSpeed = true;
break;
case "velocity":
method = "velocityAtTime";
var isSpeed = false;
break;
default:
method = "valueAtTime";
var isSpeed = false;
break;
};
var frame = timeToFrames(time);
var controller = true;
while (controller){
var t = framesToTime(frame);
var s = !isSpeed ? Math.floor(property[method](t)[axis]) : Math.floor(property[method](t));
var prevs = !isSpeed ? Math.floor(property[method](framesToTime(frame-1))[axis]) : Math.floor(property[method](framesToTime(frame-1)));
if(frame==0){
break;
};
if(prevs!=s){
if(s==triggerValue){
controller=false;
};
};
--frame;
};
if(!controller){
t;
}else{
t=0;
};
return t;
};

Reply to this Discussion! Login or Sign Up