• Adobe After Effects Expressions

  Need to relate the drop shadow effect of a pre-comp to the Light layer of the main comp

  Posted by Rafael Ribeiro on August 4, 2012 at 8:09 pm

  I got a comopsition filled with lots of pre-comps ( imagine that a wall in 3d space is the main composition and the pre-compositions are pictures with frames – chaplets to be really clear, I think).
  The pictures are hanging on that wall, and theres a light layer in the main commposition. The chaplets ( pre-comps with pictures) have a drop shadow effect (inside the pre-comp), to give a nice look, almost realistic that there’s actually a picture inside of them.

  How can I relate the direction of the drop shadow effect inside the pre-composition, to the Light layer in the main composition?

  Thanks for reading. 🙂

  Dan Ebberts replied 14 years, 1 month ago 2 Members · 5 Replies
• 5 Replies

• 

  Dan Ebberts

  August 4, 2012 at 9:09 pm

  If you’re using the Drop Shadow effect, something like this should work:

  L = comp(“Main Comp”).layer(thisComp.name);
  p1 = L.fromWorld(comp(“Main Comp”).layer(“Light 1”).toWorld([0,0,0]));
  p2 = toWorld(anchorPoint);
  d = p1 – p2;
  radiansToDegrees(Math.atan2(d[1],d[0]))-90

  If you’re using the drop shadow layer style, you’ll need to change the last line to this:

  -radiansToDegrees(Math.atan2(d[1],d[0]))

  Dan
• 

  Rafael Ribeiro

  August 4, 2012 at 9:42 pm

  neither of the expressions worked. I moved the light around but the shadow of the pre-comp did not follow it’s movement at all.

  What did I do wrong (haha) ?
• 

  Dan Ebberts

  August 4, 2012 at 10:02 pm

  The drop shadow is applied to a layer inside the precomp, correct? Or is the drop shadow applied to the precomp as a layer inside the main comp?

  Dan
• 

  Rafael Ribeiro

  August 4, 2012 at 10:10 pm

  it is applied to a layer inside the pre-comp, yes.
  I didn’t get any code errors or anything. But the drop shadow won’t move as the “Light 1” layer moves too.
• 

  Dan Ebberts

  August 4, 2012 at 10:15 pm

  I’m stumped. It works here. I must have something set up differently than you do…

  Dan

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