• Adobe After Effects

  Motion Tracking Trapcode Lux

  Posted by Andrea Stewart on February 27, 2008 at 3:47 pm

  I’m trying to set up a spotlight to shine at a point in a 2D layer to simulate a kleig light at a movie opening. I have created a camera move that follows the helicopter aerial pan of the “theater” so that I can have a 3D object floating in front of it. The camera move is not a motion track, just an approximation.

  Anyway, I’ve created two spots in Lux and tracked a spot on the 2D layer where I want the kleig lights to attach, but I can’t apply a motion track to a light it seems. When I try to attach to a Null that is parent of the light, it doesn’t put the light anywhere near my attach point. I’m supposing because the track is on a 2D layer but my light is in 3D space.

  Any suggestions? I didn’t want to make the background video 3D because I don’t want to degrade video quality.

  Andrea Stewart
  Producer/Editor/Director – Owner
  Germane Creative LLC

  Darby Edelen replied 18 years, 2 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Andrea Stewart

  February 27, 2008 at 7:13 pm

  Can I come work for you Dave? You always have a good answer. I’ll give the precomping a try.

  Andrea Stewart
  Producer/Editor/Director – Owner
  Germane Creative LLC
• 

  Darby Edelen

  February 27, 2008 at 9:46 pm

  Unfortunately it’s not possible to change a 2D position into a 3D position without having a surface in 3D that you want to project that 2D position onto… Confused yet? =)

  With a 2D position you have only X and Y values, you’re missing the Z. You can obtain a Z value if you project the X and Y values onto the plane of a 3D layer using an expression applied to the light’s Point of Interest:

  
l = thisComp.layer("TrackedNull");
td = thisComp.layer("3DLayer");

  td.toWorld(td.fromCompToSurface(l.toComp(l.anchorPoint)));


  So in addition to your camera move approximation, you would also need an approximation of the wall/plane you want to project the light onto as a solid (the “3DLayer” layer). The downside of this method is that you will receive an error immediately if your 2D layer ever moves off of the plane of the 3D layer because the 2D coord cannot be projected onto the 3D layer where the layer doesn’t exist (scale your 3D layer up A LOT to compensate).

  All in all it might be better to approximate.

  Darby Edelen
  Designer
  Left Coast Digital
  Santa Cruz, CA

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