Return-Path: Received: from mail-lb0-f176.google.com ([209.85.217.176] verified) by media-motion.tv (CommuniGate Pro SMTP 4.2.10) with ESMTP-TLS id 5284930 for AE-List@media-motion.tv; Wed, 13 Nov 2013 19:56:00 +0100 Received: by mail-lb0-f176.google.com with SMTP id p9so710849lbv.35 for ; Wed, 13 Nov 2013 10:57:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :content-type; bh=ZGyUOfTHxHannT15zg6xxWYdLcgL4npYNtWfxpEYHR8=; b=MXmZovJ/tGqRS/3xcQzYP363UzaJkoQST3Oy/jM1fwkDjg425vahBEo4CSDHz/fFTr fVUQRYviRR4cITFADjI4G2r/FJHEjegzi3Vn+NfnC1wMrpSz5DE4ZtKTPSHLLjM2lRJt bVj1yIt4tYkxdGYA//towcKvrV0T8hzHP3EFHOrBt5GFCS2PdWN1OYhjyH8FaxV5iH6G DxMnQjinKUINjqyPCgYGoChO9GCLGlSMqFqvnPfoPiKbpCZUIexpsMARvhb/gLZxuJAp vPMhT3FtUoiPNyDG3dQ9m1fH9uFRWAWWmpSY1lMPl7JIfXJICgcR0KkE5M29+R8Ey8dW db5Q== X-Received: by 10.152.20.202 with SMTP id p10mr13377lae.69.1384369068126; Wed, 13 Nov 2013 10:57:48 -0800 (PST) MIME-Version: 1.0 Received: by 10.152.3.134 with HTTP; Wed, 13 Nov 2013 10:57:28 -0800 (PST) In-Reply-To: References: From: Byron Nash Date: Wed, 13 Nov 2013 13:57:28 -0500 Message-ID: Subject: Re: [AE] freeze frame from precomp - expression needed to not get duplicates To: After Effects Mail List Content-Type: multipart/alternative; boundary=089e01493f5c8b486804eb138a5c --089e01493f5c8b486804eb138a5c Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable I've written something like this in script form(Fisher-Yates) although I did not know it had a name. I can't think of a good way to do it with expressions without killing the render. It would need to go through many iterations for each layer on each frame to get it going. I imagine with 125 layers you would start to get speed issues. On Wed, Nov 13, 2013 at 6:35 AM, Chris Zwar wrote: > Grrr sorry, I decided to google my own suggestion and discovered I was > wrong. What you need is a Fisher-Yates algorithm: > > http://en.wikipedia.org/wiki/Fisher=96Yates_shuffle > > Luckily there's plenty of examples on the web, and it seems that writing = a > script to shuffle cards is a common task given to computer students, so i= f > you think of your 300+ faces as a deck of 300 cards then you should be ab= le > to google a solution sooner or later. > > > -Chris > > > On 13/11/2013, at 10:23 PM, Chris Zwar wrote: > > This question has come up before, and I remember someone else explaining > that you will need to use a custom random number generator, and not just > the generic random expression. As you have realised, the problem with > random() is that even though the numbers are random there is nothing to > stop the same number being randomly chosen more than once. > > You need to use a "monte carlo" random number expression, which I don't > have and am not sure where you find one. I think the algorithm is normal= ly > used to shuffle a deck of cards, hence the name. I guess when you want a > computer to create a random deck of cards it's important to know that eac= h > card only appears once! > > It might be quicker to do it manually. > > HTH > -Chris > > On 13/11/2013, at 9:18 AM, Greg Balint wrote: > > Got a quick one here.. something i'm probably just either not familiar > with, or I'm thinking too hard about it. > > I've got a large grid wall of squares with people's faces in them. Each > face panel is the same precomp with this expression in the time-remap > attribute. > > seedRandom(index,true); > myFrame =3D Math.floor(random(303)); > framesToTime(myFrame) > > Basically this grabs a random frame from the precomp, which is about 10 > seconds long, and shows it as a freeze frame for that particular layer. > > I've got 125 face panels all using this expression, and for the most part > it works wonderfully.. they all have random faces on them, and if I add > another layer, the random seed changes and I get a whole new slew of face= s > (which doesn't matter in this instance, but i could see that as a problem > in others) > > My issue is, even though I've got over 300 frames (each frame with a new > face) in my precomp.. the randomness is grabbing duplicates.. in some cas= es > 2-3 pairs of duplicates over the course of the 125 it chooses. > > > Anyone know of a way to append this script so that it does not choose > something it has already? > > I'd even be fine if there were a way to use an expression to grab frames > sequentially from the precomp and then I could just hand choose to make > sure there's no duplicates in the first 125 frames. > > I think i might just be overthinking this, but I'm not sure if I've seen = a > "check for duplicate and don't use" sort of expression before. > > thanks in advance. > > -- > > ///Greg Balint > //Art Director / Motion Graphics Designer > /321.514.4839delRAZOR.com/ > > > > --089e01493f5c8b486804eb138a5c Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable
I've written something like this in script form(Fisher= -Yates) although I did not know it had a name. I can't think of a good = way to do it with expressions without killing the render. It would need to = go through many iterations for each layer on each frame to get it going. I = imagine with 125 layers you would start to get speed issues.


On Wed, Nov 1= 3, 2013 at 6:35 AM, Chris Zwar <chris@chriszwar.com> wrote= :
Grrr sorry, I decided to google my own = suggestion and discovered I was wrong. =A0What you need is a Fisher-Yates a= lgorithm:


Luckily there's plenty of examples on the web, and = it seems that writing a script to shuffle cards is a common task given to c= omputer students, so if you think of your 300+ faces as a deck of 300 cards= then you should be able to google a solution sooner or later.


-Chris<= /font>


On 13= /11/2013, at 10:23 PM, Chris Zwar <chris@chriszwar.com> wrote:

This ques= tion has come up before, and I remember someone else explaining that you wi= ll need to use a custom random number generator, and not just the generic r= andom expression. =A0As you have realised, the problem with random() is tha= t even though the numbers are random there is nothing to stop the same numb= er being randomly chosen more than once.

You need to use a "monte carlo" random number expr= ession, which I don't have and am not sure where you find one. =A0I thi= nk the algorithm is normally used to shuffle a deck of cards, hence the nam= e. =A0I guess when you want a computer to create a random deck of cards it&= #39;s important to know that each card only appears once!

It might be quicker to do it manually.

HTH
-Chris

On 13/11/2013, at 9:18 AM, = Greg Balint <delrazoraelist@gmail.com> wrote:

Got a quick one here.. somet= hing i'm probably just either not familiar with, or I'm thinking to= o hard about it.

I've got a large grid wall of squar= es with people's faces in them. =A0Each face panel is the same precomp = with this expression in the time-remap attribute.

seedRandom(index,true);
myFrame =3D Math= .floor(random(303));
framesToTime(myFrame)

Basically this grabs a random frame from the precomp, which is about 10 = seconds long, and shows it as a freeze frame for that particular layer.

I've got 125 face panels all using this expression,= and for the most part it works wonderfully.. they all have random faces on= them, and if I add another layer, the random seed changes and I get a whol= e new slew of faces (which doesn't matter in this instance, but i could= see that as a problem in others)

My issue is, even though I've got over 300 frames (= each frame with a new face) in my precomp.. the randomness is grabbing dupl= icates.. in some cases 2-3 pairs of duplicates over the course of the 125 i= t chooses.


Anyone know of a way to append this scri= pt so that it does not choose something it has already?

I'd even be fine if there were a way to use an expression to grab= frames sequentially from the precomp and then I could just hand choose to = make sure there's no duplicates in the first 125 frames.

I think i might just be overthinking this, but I'm = not sure if I've seen a "check for duplicate and don't use&quo= t; sort of expression before.

thanks in advance.

-- 
///Greg Balint
//Art Director / Motion Graphics Designer
/321.=
514.4839
delRAZOR.com/



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