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M
matteociaociao
Inspiring
February 22, 2014
Question

inertial bounce expression

  • February 22, 2014
  • 2 replies
  • 4688 views

hello everyone i have after effects cc and windows 8.

when i was on ae cs6 i used this expression and it worked perfectly

n = 0;

if (numKeys > 0) {

n = nearestKey(time).index;

if (key(n).time > time){

n--;

}

}

if (n == 0) {

t = 0;

} else {

t = time - key(n).time;

}

if (n > 0){

v = velocityAtTime(key(n).time - thisComp.frameDuration/10);

amp = 5;

freq = 1.0;

decay = 5.0;

value + (v/100)*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);

}else{

value;

}

now on ae cc it works for 1 minute and then this error pops up:    (in this case i applied the expression on the position of a null object with linear velocity)

After Effects warning: an expression was disabled as a result of an error.

Error at line 19 'Position' of layer 2 ('Null 7') in comp 'Comp 4'.

invalid numeric result (divide by zero?)

how can i fix this error? that expression was very very helpful!

thx!

    This topic has been closed for replies.

    2 replies

    Dan Ebberts
    Community Expert
    Dan EbbertsCommunity Expert
    Community Expert
    February 22, 2014

    With a decay of 5, Math.exp(decay*t) will overflow at about t = 142 seconds. You could just change this line:

    if (n > 0){

    to this:

    if (n >0 && t < 10)

    and it should work fine.

    Dan

      M
      matteociaociaoAuthor
      Inspiring
      March 28, 2014

      thx guys all your solutions works perfectly fine! this was really helpfull!

      françois leroy
      françois leroy
      Inspiring
      February 22, 2014

      Hi!

      I tried the expression and have no issue...

      However, if it works fine most of the time, you can still put a "try {} catch ()" so the expression isn't disabled.

      try{ // new line

      n = 0;

      if (numKeys > 0) {

      n = nearestKey(time).index;

      if (key(n).time > time){

      n--;

      }

      }

      if (n == 0) {

      t = 0;

      } else {

      t = time - key(n).time;

      }

      if (n > 0){

      v = velocityAtTime(key(n).time - thisComp.frameDuration/10);

      amp = 5;

      freq = 1.0;

      decay = 5.0;

      value + (v/100)*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t); //the error probably comes from here as it is the only division...

      }else{

      value;

      }

      }catch(e){value} // new line

      Cheers,

      François

      UQg
      UQg
      Legend
      February 22, 2014

      Hi, it's probably because of the Math.exp.

      You can try replacing value + (v/100)*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t); by

      value + (v/100)*amp*Math.sin(freq*t*2*Math.PI) * Math.exp(-decay*t);

      Alternatively replace

      amp = 5;

      freq = 1.0;

      decay = 5.0;

      value + (v/100)*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);

      by

      amp = 5;

      freq = 1.0;

      decay = 5.0;

      decay *= t;

      decay > 70 ? value : value + (v/100)*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay);

      Xavier.

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