• Adobe After Effects Expressions

  Opacity based on distance from Camera: multiple nested compositions

  Posted by Edan Dover on May 17, 2011 at 2:25 pm

  I have three comps, each nested in the previous:

  MASTER > Scene1 > SongsRow1

  Inside SongsRow1, there is a layer called “test” that I’d like to fade out as it pulls a certain distance away from the camera.

  I am having trouble using “toWorld” to navigate all these nested comps… I’m still not 100% clear on how “toWorld” works. This is what I have (in the opacity field of layer “test”):

  
startFade = thisComp.layer("controls").effect("startfade")("Slider");
endFade = thisComp.layer("controls").effect("endfade")("Slider");
C = comp("MASTER").activeCamera.toWorld([0,0,0]);
P = comp("MASTER").layer("Scene1").toWorld(comp("Scene1").layer("SongsRow1").toWorld(thisComp.layer("test").anchorPoint)); // This is where the problem is, I think
d = length(C,P);
linear(d,startFade,endFade,100,0)

  Thanks!

  Dan Ebberts replied 15 years, 3 months ago 2 Members · 5 Replies
• 5 Replies

• 

  Dan Ebberts

  May 17, 2011 at 3:15 pm

  I think it’s easier to do each transform as a separate step. I haven’t tested this, but I’d try it this way:

  startFade = thisComp.layer(“controls”).effect(“startfade”)(“Slider”);
  endFade = thisComp.layer(“controls”).effect(“endfade”)(“Slider”);
  C = comp(“MASTER”).activeCamera.toWorld([0,0,0]);
  P1 = toWorld(anchorPoint); // convert test postion to SongsRow1 world space
  L2 = comp(“Scene1”).layer(“SongsRow1”);
  P2 = L2.toWorld(P1); // convert P1 to Scene1 world space
  L3 = comp(“MASTER”).layer(“Scene1”);
  P3 = L3.toWorld(P2); // convert P2 to MASTER world space
  d = length(C,P3);
  linear(d,startFade,endFade,100,0)

  Dan
• 

  Edan Dover

  May 17, 2011 at 4:13 pm

  Hey Dan, first, thanks for your help!

  Does your code account for if one of the parent compositions are moving? I tried it and I’m getting a result, but “d” only wiggles between 520 and 560 (due to a wiggle in the camera position), where in actuality that value should move from 0 to 10,000, because “SongsRow1” is moving further and further away from the camera..
• 

  Dan Ebberts

  May 17, 2011 at 4:33 pm

  It should. Are all of your “Collapse Transformation” switches turned on?

  Dan
• 

  Edan Dover

  May 17, 2011 at 6:37 pm

  yes they are…
• 

  Dan Ebberts

  May 17, 2011 at 8:44 pm

  OK – I just set up the three nested comps and it seems to work fine for me. I can go into any of the comps and move the nested, collapsed 3D layer around and the text fades in and out. I really don’t know why it doesn’t work for you.

  Dan

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