• Adobe After Effects

  Starting a cumulative expression based on a condition

  Posted by Matt Tillman on March 22, 2013 at 4:43 am

  Hey guys,
  I’m trying to get a cumulative expression to start when the position of another layer crosses its Y-Position value. In this case, start pushing layer2’s X-Position once layer1’s Y-Position passes it.

  Here’s what I have:

  track = thisComp.layer(“layer1”).transform.position;
  pos = transform.position;
  accum = 0;

  for(i=timeToFrames(inPoint);i<=timeToFrames(time);i++){
  if (track.valueAtTime(i)[1]<=pos[1]){
  accum += 0;
  }else{
  accum += 10;
  }
  }

  value + [accum,0];

  I can’t for the life of me figure out why this code doesn’t work. It seems to ignore the IF statement and accumulate from the very start.

  It isn’t for anything in particular, I’m just trying to get it to work as a concept.

  Any help would be greatly appreciated.

  Roland R. kahlenberg replied 13 years, 1 month ago 3 Members · 4 Replies
• 4 Replies

• 

  Roland R. kahlenberg

  March 22, 2013 at 6:12 am

  Expressions do not retain values. You can pass on the value to an invisible textbox and recall the value with a textString argument. I suggest that you post your Q at the COW’s AE Expressions Forum.

  HTH
  RoRK

  Intensive mocha & AE Training in Singapore and Other Dangerous Locations

  Imagineer Systems (mocha) Certified Instructor
  & Adobe After Effects ACE/ACI (version 7)
• 

  Darby Edelen

  March 22, 2013 at 6:25 am

  Try changing this line:

  if (track.valueAtTime(i)[1]<=pos[1]){

  to a couple of lines:

  t = framesToTime(i);
  if (track.valueAtTime(t)[1]<=pos[1]){

  New/changed code is in bold.

  Darby Edelen
• 

  Matt Tillman

  March 22, 2013 at 7:26 am

  Thanks heaps Darby. I completely overlooked the fact that I was passing a frame value instead of time.
• 

  Roland R. kahlenberg

  March 24, 2013 at 12:18 am

  Good stuff Darby!

  Cheers
  RoRK

  Intensive mocha & AE Training in Singapore and Other Dangerous Locations

  Imagineer Systems (mocha) Certified Instructor
  & Adobe After Effects ACE/ACI (version 7)

Reply to this Discussion! Login or Sign Up