• Adobe After Effects Expressions

  Fade opacity of a 3D shape layer based on distance from another layer

  Posted by Kevin Lamb on March 1, 2011 at 2:01 am

  Hi.

  I have a grid of images roughly 16×16, and a Line (shape layer) snaking through the vertical and horizontal gaps of the grid until it drops out the bottom.

  I am trying to get my head around a script that would change the opacity of the images as the line passed between them, so as the line moves past the images, they would appear.

  I found the script below on the adobe website which changes the opacity of a layer depending on the distance from the camera, I tried to use a Null instead of a camera that followed the line, but with no success,

  Anyone any ideas?

  Thanks

  K

  startFade = 500; // Start fade 500 pixels from camera.
endFade = 1500; // End fade 1500 pixels from camera.
try{ // Check whether there's a camera.
C = thisComp.activeCamera.toWorld([0,0,0]);
}catch(err){ // No camera, so assume 50mm.
w = thisComp.width * thisComp.pixelAspect;
z = (w/2)/Math.tan(degreesToRadians(19.799));
C = [0,0,-z];
}
P = toWorld(anchorPoint);
d = length(C,P);
linear(d,startFade,endFade,100,0)

  Trent Armstrong replied 15 years, 6 months ago 2 Members · 1 Reply
• 1 Reply

• 

  Trent Armstrong

  March 8, 2011 at 7:32 pm

  First, make sure to apply this to the Opacity of each layer that will appear/disappear.

  Then make sure it’s looking for the Null instead of a Camera.

  Lastly, you’ll need to make sure your distances are appropriate and not too close or too far. Something like StartFade = 150 and endFade = 50. You can judge that or hook up some Expression Control Sliders.

  startFade = 150; // Start fade 300 pixels from Null 1
endFade = 50; // End fade 150 pixels from Null 1
try{ // Check whether there is a Null 1
C = thisComp.layer("Null 1").toWorld([0,0,0]);
}catch(err){ // No Null 1

  C = [thisComp.width * .5, thisComp.height * .5] // Centers effect around middle of Comp

  }
P = toWorld(anchorPoint);
d = length(C,P);
linear(d, startFade, endFade, 100, 0)

  Trent Armstrong – Creative Cow Leader
  https://www.dallasaeug.com

Reply to this Discussion! Login or Sign Up