Need help with a Fade Transitions script
I am new to scripting so my apologies if I have made some obvious mistakes.
Also, not sure if there is already a feature in AE I don't know about that will accomplish
what I'm trying to do, but I would like to learn AdobeExtendScript and thought this was a great application for a script.
I am trying to write a script that will adjust video footage layers and keyframe opacity fades from 100% to 0% over a
length of frames determined by the user. Nothing too crazy. I tested this script with imported snippets from Premiere and
it works, kind of, but only when the first layer in the comp is part of the selected layers.
Here's the script:
//
// fadeTransitions.jsx (12/03/12)
// Copyright © 2012 Paul Kelly for Perioperative Interactive Education. All rights reserved.
// http:pkvisualization.com
//
// This script will adjust a series of layers so that the layer opacity fades
// from 100% to 0% over a length of frames determined by the user.
//
var theComp = app.project.activeItem; //set a variable equal to the active composition
if (theComp == null || (theComp instanceof CompItem) == false) // Check if item is selected and make sure it is a CompItem
{
alert("You must have at least two layers selected");
} else {
var numberOfLayers = theComp.selectedLayers.length; // set a variable equal to the total number of selected layers
if (numberOfLayers == null || numberOfLayers < 2) // make sure there are at least two layers selected
{
alert("You must have at least two layers selected");
} else {
var startLayer = prompt("First layer to be affected: ", "Layer#");
// want to eliminate this prompt and set a variable for the top-most selected layer.
// var startLayer = theComp.selectedLayers[0]; isn't working. I want the lowest indexed layer of several selected layers
fadeTransitions();
} //end second else: numberOfLayers test
} //end first else: theComp test
function fadeTransitions()
{
app.beginUndoGroup("FadeTransitions");
var overLap = parseInt(prompt("Specify length of fade-off (frames)", "0"));
overLap = overLap * theComp.frameDuration;
for (var i=1; i<=numberOfLayers; i++)
{
var layerIndex = (startLayer - 1) + i; //create layer index, subtract 1 to correct layer offset
if (layerIndex > numberOfLayers) { //end before layerIndex becomes more than numberOfLayers
alert("Fade Transitions script done");
break;
} else {
var topLayerEnd = theComp.layer(layerIndex).outPoint;
if ((layerIndex+1) > numberOfLayers) { //end before (layerIndex+1) becomes more than numberOfLayers
alert("Fade Transitions script done");
break;
} else {
var btmLayerStart = theComp.layer(layerIndex+1).inPoint;
var btmLayerEnd = theComp.layer(layerIndex+1).outPoint;
var duration = btmLayerEnd - btmLayerStart;
theComp.layer(layerIndex+1).inPoint = (topLayerEnd - overLap);
theComp.layer(layerIndex+1).outPoint = (topLayerEnd + duration);
theComp.layer(layerIndex).opacity.setValueAtTime((theComp.layer(layerIndex).outPoint - overLap), 100);
theComp.layer(layerIndex).opacity.setValueAtTime(theComp.layer(layerIndex).outPoint, 0);
} //end 2nd else
} //end 1st else
} //end for loop
app.endUndoGroup();
} //end fadeTransitions function
Problem #1: I want to eliminate the prompt asking for the startLayer, instead I want the first layer to be the top-most of
a selection of layers, so that at any point you can select a series of layers and run the script to only affect those layers.
I tried to do that by setting a variable to app.project.activeItem.selectedLayers[0]; but it didn't work. This feature would really be
necessary during later stages of compositing, when there are many layers of captions, audio, 3D rendered images, etc. above
the footage layers in the comp.
Problem #2: Unless the selected layers are pre-arranged in a cascading fashion, I get some really weird adjustments to the in-
and outPoints. Not sure what's causing this. This isn't a top priority because most of the time I will be using this script the layers
will already be arranged correctly (I am importing a sequence from Premiere Pro), but I would still like to know how I could fix this
and better understand the way ExtendScript works.
Problem #3: Right now, the way the layer inPoints are adjusted, is the same as if I hovered the mouse over the layer inPoint and
got the horizontal line with opposite-facing arrows, and click-dragged the inPoint backward, but, what I would prefer is the
equivalent of if I hover the selection tool over the middle of the layer and click-dragged the entire layer L or R, so that the inPoint
is still the same location in the footage. Like problem #2, this isn't a super big deal, I just want to better understand what's happening
in the script. I tried using startTime instead of inPoint in the script, but then it just stopped working entirely.
Any help/insights would be greatly appreciated, and everyone feel free to use what I have so far if you like.
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