• Adobe After Effects Expressions

  Mechanical fan with expression

  Posted by Mio Tanaka on January 2, 2012 at 4:51 pm

  I made a mechanical fan whose blades start rotating and keeps the same speed after 1.5 seconds using AE at work.
  Although I am still a novice at Expressions, I managed to make two versions of basically the same thing.

  Below is the expressions I made.

  (to blades’ rotation)

  1:non-split layer

  if (time <= 1.5)
  {
  thisComp.layer(“null1”).effect(“Slider Control”)(“Slider”)
  }
  else
  {
  value + time*900

  2:split layer (in point is at 1.5 seconds)
  this layer is split in two at 1.5 seconds and the expression is applied to the latter half.

  thisComp.layer(“wing01_01”).transform.rotation + (time- 1.5)*900

  Although I managed to make it, I don’t understand why I needed to subtract 1.5 seconds in the latter parentheses in the second expression.
  At first I did the opposite since the layer starts from 1.5 seconds.

  It might be pretty basic, but anyone care to explain?
  Thanks in advance.

  Mio Tanaka replied 14 years, 4 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Dan Ebberts

  January 2, 2012 at 5:53 pm

  I think it might be a happy coincidence. If you wanted to make the rotation match the slider at the transition point, I think I’d do it like this:

  
s = thisComp.layer("null1").effect("Slider Control")("Slider");
tSwitch = 1.5;

  if (time <= tSwitch)
s.value
else
s.valueAtTime(tSwitch) + (time-tSwitch)*900


  Dan
• 

  Mio Tanaka

  January 3, 2012 at 6:04 am

  Yes, it seems to be just a coincidence…
  Thank you for the clearer and wiser expression.
  It looks much more flexible.

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