[Dan Ebberts]

I don’t know of a direct way, but you might be able to come up with a hack where you make sure just that layer is selected, add add a bad expression to the path, then do something like this:

app.executeCommand(app.findMenuCommandId("Reveal Expression Errors"));

then delete the expression.

[Dan Ebberts]

Ah, that would be like this:

moveFrames = 5;
holdFrames = 15;
range = 200;
moveDur = framesToTime(moveFrames);
totalDur = framesToTime(moveFrames+holdFrames);
seed = Math.floor(time/totalDur);
t = time%totalDur;
seedRandom(seed,true);
offset1 = seed > 0 ? random([-range,-range],[range,range]) : [0,0];
p1 = value + offset1;
seedRandom(seed+1,true);
offset2 = random([-range,-range],[range,range]);
p2 = value + offset2;
linear(t,0,moveDur,p1,p2)

[Dan Ebberts]

OK, here’s an example that will wander around in the vicinity of the layer’s original position:

moveFrames = 15;
range = 200;
moveDur = framesToTime(moveFrames);
seed = Math.floor(time/moveDur);
t = time%moveDur;
seedRandom(seed,true);
offset1 = seed > 0 ? random([-range,-range],[range,range]) : [0,0];
p1 = value + offset1;
seedRandom(seed+1,true);
offset2 = random([-range,-range],[range,range]);
p2 = value + offset2;
linear(t,0,moveDur,p1,p2) // could use ease() instead

[Dan Ebberts]

Do you want the movement constrained to a particular area, or each movement constrained to a maximum amount from the previous location?

[Dan Ebberts]

Yes, something like this should work:

txt = thisComp.layer("control").text.sourceText;
eval(txt)

[Dan Ebberts]

Also, would love to know what error message you’re running into with the script.

[Dan Ebberts]

Yes, so probably like this:

tStart = inPoint;
dur = .75;
delay = .25;
t1 = tStart + delay*(thisProperty.propertyGroup(3).numProperties - thisProperty.propertyGroup(2).propertyIndex);
t2 = t1 + dur;
linear(time,t1,t2,0,100)

[Dan Ebberts]

This is just pretty rough, and likely won’t meet your exact needs, but should give you an idea of possible automation. If you apply an expression like this to the End property of each brush’s Stroke Options:

tStart = inPoint;
dur = .75;
delay = .25;
t1 = tStart + delay*(thisProperty.propertyGroup(2).propertyIndex - 1);
t2 = t1 + dur;
linear(time,t1,t2,0,100)

It will sequence the brush strokes. Then, instead of adding the expressions by hand, you could use a simple script like this to apply the expression to each brush:

function addExpression(){
	var myComp = app.project.activeItem;
	if (! (myComp && myComp instanceof CompItem)){
		alert("No comp active.");
		return;
	}
	if (myComp.selectedLayers.length == 0){
		alert ("No Layer Selected.");
		return;
	}
	var myLayer = myComp.selectedLayers[0];
	var myEffects = myLayer.property("ADBE Effect Parade");
	var myPaint;
	var myStrokes;
	var myBrush;
	var expr = 'tStart = inPoint;\r' +
	'dur = .75;\r' +
	'delay = .25;\r' +
	't1 = tStart + delay*(thisProperty.propertyGroup(2).propertyIndex - 1);\r' +
	't2 = t1 + dur;\r' +
	'linear(time,t1,t2,0,100)\r';
	for (var i = 1; i <= myEffects.numProperties; i++){
		if (myEffects.property(i).matchName == "ADBE Paint"){
			myPaint = myEffects.property("ADBE Paint");
			myStrokes = myPaint.property("ADBE Paint Group");
			for (var i = 1; i <= myStrokes.numProperties; i ++){
				if (myStrokes.property(i).matchName == "ADBE Paint Atom"){
					myStrokes.property(i).property("ADBE Paint Properties").property("ADBE Paint End").expression = expr;
				}
			}
		}
	}
}
addExpression();

I hope that’s helpful.

[Dan Ebberts]

If it needs to loop, I think I’d approach it a little differently:

p1 = [100,100];
p2 = [500,500];
spd = 100; // pixels per second
tTot = length(p1,p2)/spd;
tStart = inPoint;
t = Math.max((time-tStart)%tTot,0);
linear(t,0,tTot,p1,p2)

[Dan Ebberts]

This is a pretty general solution that should work OK. You can tie variable spd to a slider (as long as you don’t animate the slider):

p1 = [100,100];
p2 = [500,500];
spd = 100; // pixels per second
tStart = inPoint;
v = normalize(p2 - p1);
t = Math.max(time-tStart,0);
d = Math.min(spd*t, length(p1,p2));
p1 + v*d;