
AFTER EFFECTS CS3
User Guide
584
4 SelecttheBulgeeffect’sBulgeCenterpropertyintheTimelinepanelandchooseAnimation>AddExpression,or
Alt-click (Windows) or Option-click (Mac OS) the property’s stopwatch button.
5 Select the default expression text and type the following:
fromWorld(thisComp.layer("Magnifier").position)
Example: Fade a 3D layer’s opacity based on distance from camera
❖ Apply the following expression to a 3D layer’s Opacity property:
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)
The fade starts at a distance of 500 pixels from the camera and is complete at 1500 pixels from the camera. The
linear interpolation method is used to map distance values to opacity values.
See also
“Add, edit, and remove expressions” on page 549
“Create a camera layer and change camera settings” on page 176
Example: Make a 3D layer invisible if facing away from camera
❖ Apply the following expression to a 3D layer’s Opacity property:
if (toCompVec([0, 0, 1])[2] > 0 ) value else 0
See also
“Add, edit, and remove expressions” on page 549
“Create a camera layer and change camera settings” on page 176
Example: Flip layer horizontally if facing away from camera
❖ Apply the following expression to a 3D layer’s Scale property:
if (toCompVec([0, 0, 1])[2] > 0 ) value else [-value[0], value[1], value[2]]
See also
“Add, edit, and remove expressions” on page 549
“Create a camera layer and change camera settings” on page 176
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