• Adobe After Effects Expressions

  Expression to drive wiggle by velocity?

  Posted by Joel Witmer on May 21, 2010 at 8:02 pm

  Can anyone please explain how I can set the wiggle amount and frequency so that it is driven by the velocity of the camera movement? So the faster the camera moves over time, the more camera wiggle there would be and vica versa.

  I’m new to expressions so while I have an idea of what I need to do I can’t seem to figure it out exactly.

  Thanks!

  Joel Witmer replied 15 years, 11 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Darby Edelen

  May 21, 2010 at 10:24 pm

  You can access the velocity of the camera’s position with:

  thisComp.activeCamera.transform.position.velocity

  or if applied directly to the camera:

  transform.position.velocity

  or if applied directly to the camera’s position:

  velocity

  🙂

  Note that a velocity is a vector, so you will be receiving an array with 3 components (x, y and z). My guess is what you’d rather do is find the speed at which your camera is moving, which is a scalar that corresponds to the magnitude of the velocity. For speed use:

  thisComp.activeCamera.transform.position.speed

  transform.position.speed

  speed

  Once you have the speed, you can alter the value in order to end up with the frequency and amplitude of your wiggle. If applied to your camera’s position property:

  
f = linear(speed, 0, 3000, 0, 5); //as the camera's speed changes from 0 to 3000 pixels per second, increase the frequency from 0 wiggles per second to 5

  a = linear(speed, 0, 3000, 0, 50); //as the camera's speed changes from 0 to 3000 pixels per second, increase the amplitude of the wiggle from 0 to 50 pixels

  wiggle(f,a); //apply the wiggle


  This code isn’t perfect, as wiggle will change it’s results proportionally faster with the rate of change of the frequency, so you’ll actually get more shake during periods of acceleration than during periods of high speed (where there will also be a good amount of shake, but not as much as during acceleration/deceleration).

  Darby Edelen
• 

  Joel Witmer

  May 24, 2010 at 5:37 pm

  Thanks so much Darby!

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