Communigate Pro AE-List@media-motion.tv Message 48714

Hmmm... To get that expression to work, I’m guessing you’d need to use the optional time parameter for the layer space transforms and specify the same time you’re using to sample the null’s position. So, for example, if you’re getting the null’s position with valueAtTime(t), you’d have to do the same calculation for t in your orientation expression and then modify all the transforms to use it, like this:

fromWorldVec(L.toWorldVec([1,0,0],t),t);

Hard to say for sure without seeing how you have it set up.

Dan

From: Brian Behm

Sent: Sunday, April 28, 2013 2:16 PM

To: After Effects Mail List

Subject: Re: [AE] Offset along motion path?

OK. I've got that up and working. I gave the null object motion path a loopOutDuration so that I could have the driver go around and around the track. Now the next problem I'm trying to squash is how to get the object to auto-orient around the path. Normal auto orientation doesn't seem to be working since it's grabbing it's position from the slider instead of position.

Dan, I'm looking at your auto-orientation script here http://forums.adobe.com/message/5196644

(pasted for convenience)

L = thisComp.layer("other layer");

u = fromWorldVec(L.toWorldVec([1,0,0]));

v = fromWorldVec(L.toWorldVec([0,1,0]));

w = normalize(fromWorldVec(L.toWorldVec([0,0,1])));

sinb = clamp(w[0],-1,1);

b = Math.asin(sinb);

cosb = Math.cos(b);

if (Math.abs(cosb) > .0005){

c = -Math.atan2(v[0],u[0]);

a = -Math.atan2(w[1],w[2]);

}else{

a = (sinb < 0 ? -1 : 1)*Math.atan2(u[1],v[1]);

c = 0;

}

[radiansToDegrees(a),radiansToDegrees(b),radiansToDegrees(c)]

I'm not sure how to pass the value from the original expression over to the auto-orientation expression. My initial thought was to pass the value derived from the first expression over to L in the second expression. But watching what happens to L in the equation it seems like it wants the layer itself to pull coordinates from After Effects world space. Any suggestions?

Brian Behm | Art Director
Rooster Teeth Productions
636 Ralph Ablanedo
Austin, TX 78748
office 512-480-0336
mobile 512-965-7914

On Sun, Apr 28, 2013 at 3:43 PM, Brian Behm <flabbyironman@gmail.com> wrote:

that makes sense. Hadn't thought about driving it through an expression/slider combo.

Thanks, Dan.

Brian

On Sun, Apr 28, 2013 at 3:38 PM, Dan Ebberts <debberts@comcast.net> wrote:

If you paste the path into a Null’s position, you’ll get a motion path with a duration of 2 seconds. Then if you have a slider going from 0 to 100 to represent percentage of travel along the path, you can you use an expression like this for your triangle:

s = (your slider value);

thisComp.layer(“Null 1”).transform.position.valueAtTime(2*s/100)

Something like that.

Dan

From: Brian Behm

Sent: Sunday, April 28, 2013 1:28 PM

To: After Effects Mail List

Subject: [AE] Offset along motion path?

Hey everybody,
quick question that's been confounding me. I have a race track simulation I'm developing for an info graphic and I have two representative triangles that I want to animate along the path. Because they're going different speeds, I want to be able to parent them to the path but not lock them into a specific time so that I can animate the offset along the path. Sort of like how Trapcode 3D stroke can animate along a portion of the path.

I know I can paste motion paths into After Effects, but that doesn't solve what I want it to do. Is there a way to constrain motion to a path without constraining it to a specific time?

Brian

Brian Behm | Art Director
Rooster Teeth Productions
636 Ralph Ablanedo
Austin, TX 78748
office 512-480-0336
mobile 512-965-7914

--
not getting enough of my blather?
check out http://flabbyironman.blogspot.com
or my portfolio at http://behmcreative.com

--
not getting enough of my blather?
check out http://flabbyironman.blogspot.com
or my portfolio at http://behmcreative.com