• Adobe After Effects Expressions

  Tracking Data and Animation

  Posted by Fede Berg on March 13, 2012 at 9:36 pm

  Hello people:

  I have this hand-held footage and i want to add an animated lightstreak to it.
  So far I have the lightstreak and it’s animation. I followed Andy Kramer’s Lightstreak tutorial on VideoCopilot.net.

  Right now i have 5 layers:
  1- A camera
  2- A 1-frame composition (visibility off)
  3- A null object with it’s position animated.
  4- A Black Solid with Trapcode Particular applied to it.
  The emitter is set to the null in layer 3 and the texture of the particle is the comp in Layer 2.
  5- My hand-held video.

  You can now see the lightstreak appear and move across the screen on top of my video, it doesn’t look good because of the movement on the video.

  Next thing I do is Motion track the video, but when I apply the track data to the null it just erases the animation. So i applied the data to a new null object (named TrackData)

  I tried to come up with an expression that adds to my layer 3’s position the value of TrackData’s position and then subtracks the value of TrackData’s position at frame 1.

  My brain hurts, Please help me
  Which would be the expression i want? or, Is there an easier way to do this?

  Fede Berg replied 14 years, 2 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Dan Ebberts

  March 15, 2012 at 1:29 am

  Couldn’t you just parent layer 3 to TrackData?

  Dan
• 

  Fede Berg

  March 15, 2012 at 1:39 am

  I tried that but it messes with the lightstreak animation. Thanks for your reply anyway!

  But today I had an epiphany.
  Instead of complicating everything with expressions I should have the lightstreak on a comp (“lightstreak”) and then in a new comp I can add “lightstreak” as a layer as well as the video. Then i can do the motion tracking as usual.
  I haven’t tried it yet, but i think it should work, Right?

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