• Adobe After Effects

  Expressions and relative space

  Posted by Scott Hathaway on October 3, 2006 at 4:56 am

  Hello all,

  This is my first attempt at expressions since up to now I have tried my hardest to avoid them but it seems I might need to use one this time. Whew.

  I have some plain video and I want to place a photoshop layer on top of that video while giving the appearance that the layer is a part of the video. The camera was almost completely locked down when I shot the footgae but it was on my shoulder so there was a little weave. So what I did to counteract that weave was create a small 20×20 red square and did frame by frame position animations based on a reference point in the video in order to get positions that correspond to the minute weaving. Now I want to take those positions and use them as reference points for my layer that will be at some other spot in the frame, not where I positioned the red square. When I tried a pickwhip expression to link the photoshop layer’s position to the red square’s position, it did just that, it moved my layer right on top of the red square. How can I put the layer where I want it and still have it move around the frame little by little like I animated the red square?

  Mike Clasby replied 19 years, 7 months ago 3 Members · 3 Replies
• 3 Replies

• 

  Adolfo Rozenfeld

  October 3, 2006 at 5:10 am

  If I understood correctly, you don’t need expressions at all for this. You only need to set the video layer as a parent for the other layer. At any spot in time, place the second layer in the relative position you like and set the first one as the parent. As a consequence, before and after that spot, the second layer will move in tandem with the first one, in a relative way.
  Next time, you don’t need to correct manually the camera motion. After Effects’ motion tracking/stabilizing technology can do that for you, in an automated (or at least, semi automated) manner.
  Hope this helps.

  Adolfo Rozenfeld
  Buenos Aires – Argentina
  https://www.adolforozenfeld.com
  adolfo(AT)adolforozenfeld.com
• 

  Scott Hathaway

  October 3, 2006 at 7:06 am

  Well, the video layer isn’t being animated. As far as the computer is concerned, that video’s boundaries aren’t moving so it would be like parenting to a null, immobile layer. I considered this but to my understanding, nothing will happen… I gave your idea a shot but nothing of consequence happened. But I will try track motion. Thank you. More suggestions?
• 

  Mike Clasby

  October 3, 2006 at 5:12 pm

  This from Adobe stablizes old footage, “Old-time movie revival hour”:

  https://studio.adobe.com/us/tips/tip.jsp?p=1&id=100899&xml=aft65sdrotoscope

  Aharon steps though Motion Tracking an eye to a cartoon face, starts at about the 5 minute mark, you can see details of fixing a cranky track, here:

  https://forums.creativecow.net/cgi-bin/new_page_wrapper.cgi?forumid=2&page=https://www.creativecow.net/articles/rabinowitz_aharon/cartoon_look/index.html

  movie here:

  https://forums.creativecow.net/articles/rabinowitz_aharon/cartoon_look/CC_LiveTrace_Pt_3CD.mov

  These from Adobe use the Tracker to afix layers to footage, but might also be useful.

  Keep motion in perspective –
  https://studio.adobe.com/us/tips/tip.jsp?p=1&id=100241&xml=aft65cornerpin

  Track It

  https://studio.adobe.com/us/tips/tip.jsp?p=1&id=100362&xml=ae65tttrack

  Using the new Motion Tracker

  https://studio.adobe.com/us/tips/tip.jsp?p=1&id=487&xml=aft6ttmotiontracker

  Tracking obscured objects in video

  https://studio.adobe.com/us/tips/tip.jsp?p=1&id=399&xml=aft6tracking

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