• Adobe After Effects Expressions

  Wiggling in Particular

  Posted by Nick Hill on April 4, 2008 at 11:24 am

  Hi all

  I’m trying to get some light streaks (as in Andrew Kramer’s great tutorial) to wiggle around the position of a null object in Particular. My expression is this:

  x = thisComp.layer(“EmitNull”).transform.position[0];
  y = thisComp.layer(“EmitNull”).transform.position[1];
  wa = thisComp.layer(“EmitNull”).effect(“WiggleAmt”)(“Slider”);
  wf = thisComp.layer(“EmitNull”).effect(“WiggleFreq”)(“Slider”);
  w = wiggle(wf, wa);
  x += w[0];
  y += w[1];
  [x, y]

  WiggleAmt and WiggleFreq are just two sliders I set up to make things easier to control. This works, *BUT* for some reason the light streaks appear about 345 pixels to the right of the null object. Nothing’s parented to anything else. The comp is 836 x 24 pixels and it doesn’t seem to affect the Y position. Any ideas?

  Cheers

  Nick

  Nick Hill replied 18 years, 1 month ago 2 Members · 2 Replies
• 2 Replies

• 

  Dan Ebberts

  April 4, 2008 at 1:15 pm

  The problem is that if you don’t specify a property to wiggle the result of wiggle() includes the value of the property you have the expression is applied to. So you can either subtract that out, like this:

  x = thisComp.layer(“EmitNull”).transform.position[0];
  y = thisComp.layer(“EmitNull”).transform.position[1];
  wa = thisComp.layer(“EmitNull”).effect(“WiggleAmt”)(“Slider”);
  wf = thisComp.layer(“EmitNull”).effect(“WiggleFreq”)(“Slider”);
  w = wiggle(wf, wa) – value;
  x += w[0];
  y += w[1];
  [x, y]

  Or just wiggle the emitter’s position directly, like this:

  P = thisComp.layer(“EmitNull”).transform.position;
  wa = thisComp.layer(“EmitNull”).effect(“WiggleAmt”)(“Slider”);
  wf = thisComp.layer(“EmitNull”).effect(“WiggleFreq”)(“Slider”);
  P.wiggle(wf, wa);

  Dan
• 

  Nick Hill

  April 5, 2008 at 1:15 pm

  Aha – I thought it’d be something like that. Thanks very much for demystifying!

  Cheers

  Nick

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