View Full Version : Importing Alpha Data for a layer

09 September 2002, 07:21 PM

Im new to AfterEffects (although not to the subject in general) and have a burning quesiton.

I have a video containing some scrolling text (think: movie credits) and another containing a background (think: shot of rippling water). Both were rendered with 3DStudio and for reasons to do with 3DStudio I need to merge them with Aftereffects.

So, in other words I need to put the text "onto" the background video. The trouble is, I cant figure out how to get alpha data for the text. Thus far, the best I have been able to do is just put the text and background into a composition and set the text opacity to 50% which isnt very good.

I tried rendering the text from 3DStudio in a range of formats hoping that Alpha data would be saved with the video, but no luck.

My question is this: How can I render the text video ontop of the background video using the texts RGB as the alpha, or by importing a rendering of the texts alpha?

Thanks for any help :cool:

09 September 2002, 11:50 AM
if you render the alpha seperately you can place the clip ontop of the text layer and then select the text layer and choose track matte -> luma matte. this will work!
but you should also check if it is really impossible to render an RGBA image from 3DS (makes things much easier!)? Have you checked in photoshop if your renders have an alpha channel? if yes, it seems like you?ve choosen the wrong option when importing your footage. it should be "alpha integrated - premultiplied with:". Maybe that?s why it doesn?t work!
Hope i coud help!

10 October 2002, 06:59 PM
I dont know which format to render the video in which will include the alpha channel. I tried a range, but when imported into AE they simply had all white alpha data. There doesnt seem to be any options regarding importing the alpha data in the File->Import dialog box... :(

Am I using a different version of AE to you? Im on 5.5, I couldnt find the Alpha Matte bit you mentioned either...

10 October 2002, 09:11 PM
i'm using 5.5 too, so i guess iīll have to specify what i said, the track matte can be found (when the layer is selected) under layer -> track matte -> luma matte (eventually inverted). iīm using a german version so maybe itīs due to my translation but i think it has to be called like this.

for the import dialog: if it doesnīt appear the footage has no recognized alpha. have you tried rendering tiffs or tgas? i donīt have 3d studio so i canīt tell where you can switch the alpha on/off but look for something with 24bit/32bit and choose 32.
you can also access this ae dialogue when selecting the footage and pressing ctrl+F (footage controls). there you can (if you have an alpha channel) specify how to use it if you didnīt at import?

i hope i was a bit clearer this time

Ian Jones
10 October 2002, 05:15 AM
Hi there,

You can render an alpha channel with 3ds max 4 (which I'm using) by going to rendering > render. The box pops up, the thing is that you don;t realise that there are actually staxx more option in this box. Go ahead and click on the scrollbar on the right hand side, you'll discover extra menus you probably didnt realise were there. I missed them for several weeks before stumbling across them by accident.

You want the render elements tab. Add an element and select alpha. You should be able to figure out the rest, I haven't actually tried it myself yet.

Hope that helps.

10 October 2002, 12:14 AM
render out to TIFF, TGA or PNG (my format of choise) then check
the ALPHA in the popup option window.
in the AFX while you are importing the footages it will ask you
about how to import the alpha channel. just select second line.
it should work. if there is a problem again, write more details
about what you are doing. (or maybe you renderd the texts &
the BG in a same scene/view?! don't tell me you did it! ;) )

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