Return-Path: Received: from gateway02.websitewelcome.com ([67.18.66.20] verified) by media-motion.tv (CommuniGate Pro SMTP 4.2.10) with ESMTP id 4781004 for AE-List@media-motion.tv; Fri, 20 Jul 2012 18:18:31 +0200 Received: by gateway02.websitewelcome.com (Postfix, from userid 5007) id 1A5E6BDA623D7; Fri, 20 Jul 2012 11:22:23 -0500 (CDT) Received: from alpina.websitewelcome.com (alpina.websitewelcome.com [74.54.176.2]) by gateway02.websitewelcome.com (Postfix) with ESMTP id D0D9EBDA6237C for ; Fri, 20 Jul 2012 11:22:22 -0500 (CDT) Received: from [199.21.106.94] (port=52430 helo=[192.168.0.5]) by alpina.websitewelcome.com with esmtpsa (TLSv1:AES128-SHA:128) (Exim 4.77) (envelope-from ) id 1SsFy9-0007bO-1P for AE-List@media-motion.tv; Fri, 20 Jul 2012 11:22:21 -0500 From: Chris Meyer Mime-Version: 1.0 (Apple Message framework v1278) Content-Type: multipart/alternative; boundary="Apple-Mail=_8A157F2C-13FC-4759-807A-7E58AB428037" Subject: Re: [AE] Issue with Transparency in CS6 Raytracing Date: Fri, 20 Jul 2012 10:22:19 -0600 In-Reply-To: To: After Effects Mail List References: Message-Id: <61657382-9790-42C2-B6DC-912594200041@crishdesign.com> X-Mailer: Apple Mail (2.1278) X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - alpina.websitewelcome.com X-AntiAbuse: Original Domain - media-motion.tv X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - crishdesign.com X-BWhitelist: no X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: ([192.168.0.5]) [199.21.106.94]:52430 X-Source-Auth: chris@crishdesign.com X-Email-Count: 1 X-Source-Cap: Y3Jpc2h3ZWI7Y3Jpc2h3ZWI7YWxwaW5hLndlYnNpdGV3ZWxjb21lLmNvbQ== --Apple-Mail=_8A157F2C-13FC-4759-807A-7E58AB428037 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=iso-8859-1 A subtle but important point in CS6 with ray tracing is to distinguish = between Opacity and Transparency. Opacity alters the alpha channel for a layer; Transparency does not. If = you create some extruded text in an otherwise blank comp, and either = move the cursor across it while watching the RGBA values in the Info = panel (or simply toggle on the Transparency Grid), you'll observe that a = fully-transparent object with Opacity =3D 100% has an alpha value of = 100% and does not pass the transparency grid through. Now, an admittedly confusing (but often desirable) quirk in CS6 is that = if you place a 2D layer behind this transparent 3D layer _inside the = same composition_, you can "look through" the transparent-but-opaque 3D = layer and see the 2D layer. (It won't be refracted - only 3D layers get = refracted by other 3D layers - but you'll see it.) So if you want to create a transparent object in AE, and render with an = alpha that represents this "transparency", you'll need to fake it. What = I used to do in dedicated 3D programs (which often have the same quirk) = is render a second alpha-only pass and reduce the opacity of the = semi-transparent objects just for that pass. You might get a better fake = by placing a black solid behind, rendering the RGB, and converting that = RGB pass into a grayscale alpha channel; this will show the effects of = Transparency Rolloff. But I agree that it would be a nice feature request for AE to allow = exporting of an alpha channel that matches what it does internally if = there is a 2D layer behind in the same composition. In the meantime, = think of it as being like exporting a layer with a blending mode: The = blending mode only interacts with layers inside the same composition; = not with layers composited outside the program. hope that helps - Chris =20 On Jul 20, 2012, at 8:31 AM, mylenium@mylenium.de wrote: > Either it's a design feature (set Alpha to opaque to avoid degenerate = generate colors with premultiplied backgrounds) or a bug (premature = termination of the ray evaluation). Whatever it is, probably nothing you = can fix. > =20 > Mylenium > [Pour Myl=E8ne, ange sur terre] > ----------------------------------------- > www.mylenium.de >=20 >=20 >=20 > "S=E9bastien" hat am 20. Juli 2012 um 14:46 = geschrieben:=20 >=20 > Hi gang,=20 >=20 > I have to export the alpha channel of my comp, nothing really fancy at = first, but then I noticed that my semi-transparent extruded shape = objects are considered opaque.=20 >=20 > You can see here on my screenshot: = https://www.dropbox.com/s/1f4u9v85d54sw7w/transparency.png The selected = object is 45% opaque, and I should somehow see the checkboard through = it, but no, the transparency is filled with some default black = environment.=20 >=20 > At first I thought it was because my difraction was at 1.5 but no = matter what value I change, it's always looking opaque when I put it = against a transparent background (when I put an object behind it behaves = correctly, it's only when the bg is transparent.=20 >=20 > Any idea how to circumvent this ? Is it intended behavior ? (i'm quite = new to Raytracing)=20 >=20 > Thanks !=20 >=20 > Cheers,=20 >=20 > Seb=20 >=20 > --=20 > S=E9bastien=20 >=20 > L'ebook que Nicolas ne trouve pas tr=E8s dr=F4le, mais que tout le = monde adore=20 > politikaillera.fr >=20 > =20 --Apple-Mail=_8A157F2C-13FC-4759-807A-7E58AB428037 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=iso-8859-1 A = subtle but important point in CS6 with ray tracing is to distinguish = between Opacity and Transparency.

Opacity alters the = alpha channel for a layer; Transparency does not. If you create some = extruded text in an otherwise blank comp, and either move the cursor = across it while watching the RGBA values in the Info panel (or simply = toggle on the Transparency Grid), you'll observe that a = fully-transparent object with Opacity =3D 100% has an alpha value of = 100% and does not pass the transparency grid = through.

Now, an admittedly confusing (but = often desirable) quirk in CS6 is that if you place a 2D layer behind = this transparent 3D layer _inside the same composition_, you can "look = through" the transparent-but-opaque 3D layer and see the 2D layer. (It = won't be refracted - only 3D layers get refracted by other 3D layers - = but you'll see it.)

So if you want to create a = transparent object in AE, and render with an alpha that represents this = "transparency", you'll need to fake it. What I used to do in dedicated = 3D programs (which often have the same quirk) is render a second = alpha-only pass and reduce the opacity of the semi-transparent objects = just for that pass. You might get a better fake by placing a black solid = behind, rendering the RGB, and converting that RGB pass into a grayscale = alpha channel; this will show the effects of Transparency = Rolloff.

But I agree that it would be a nice = feature request for AE to allow exporting of an alpha channel that = matches what it does internally if there is a 2D layer behind in the = same composition. In the meantime, think of it as being like exporting a = layer with a blending mode: The blending mode only interacts with layers = inside the same composition; not with layers composited outside the = program.

hope that helps = -
Chris


 

On Jul 20, 2012, at 8:31 AM, mylenium@mylenium.de = wrote:

Either it's a design feature (set Alpha = to opaque to avoid degenerate generate colors with premultiplied = backgrounds) or a bug (premature termination of the ray evaluation). = Whatever it is, probably nothing you can fix.

 

Mylenium

[Pour Myl=E8ne, ange sur = terre]
-----------------------------------------
www.mylenium.de

=20
=20

"S=E9bastien" <yenaphe@gmail.com> hat am 20. = Juli 2012 um 14:46 geschrieben:

=20
=20
Hi gang,

I have to export the alpha channel of my comp, nothing really = fancy at first, but then I noticed that my semi-transparent extruded = shape objects are considered opaque.

You can see here on my screenshot:=20 https:= //www.dropbox.com/s/1f4u9v85d54sw7w/transparency.png The selected = object is 45% opaque, and I should somehow see the checkboard through = it, but no, the transparency is filled with some default black = environment.
=20
At first I thought it was because my difraction was at 1.5 but = no matter what value I change, it's always looking opaque when I put it = against a transparent background (when I put an object behind it behaves = correctly, it's only when the bg is transparent.
=20
Any idea how to circumvent this ? Is it intended behavior ? = (i'm quite new to Raytracing)

Thanks !

Cheers,

Seb

--=20
S=E9bastien

L'ebook que Nicolas ne trouve pas tr=E8s dr=F4le, mais que = tout le monde adore
=20 politikaillera.fr
=20
 
=20
=20
=20 =20

= --Apple-Mail=_8A157F2C-13FC-4759-807A-7E58AB428037--