calling all Aftereffects pros: HEEELP!!

[super gnu]

my client has asked for a prores final export, WITH ALPHA CHANNEL, for my project, which is a can and water droplets on a coloured bg.


the afx comp has many layers with different blending modes etc.. not all have transparency obviously.. many are screen/overlay/multiply, which are "transparent" due to the blending modes.


how on earth do i generate an alpha channel for the whole thing?

i thoought maybe turning off the bg layer and rendering with alpha might do it, but the layers set to screen(for example) are treated as solid in the alpha even if they are transparent in all black areas in the actual comp.


how to do it? this is quite urgent..

[joconnell]

Make your bg black, put a fill effect on every layer to make it white, you'll end up with something that looks like an alpha. You might need to change the mids of some layers after to make it resemble the intensity levels you see in your comp.

[super gnu]

that was a suggestion i saw, but wont the edges and transparencies be all off? and what about the layers with blending modes on them? its no good if i have fringes round everything.. the mind boggles if this is the proper way to do it.. given i can happily place a bg in the comp without fringing, there *should* be a way to "collapse" the transparency down.. or something..?

[joconnell]

Yep, you'll have to fake the alpha for all of your screens and overlays. The fringing thing is a pain in the ass too as you've no idea how they're going to use it or the skill level of the person who'll take it over. I'd also make sure what you supply is rendered against black, a lot of softwares (nuke included) assume that things are blended against black and when they use the alpha to remove the background colour from your semi transparent bits it may go a bit weird looking.

[super gnu]

they have asked for a prores with alpha as the final delivery, because they want the option to switch background or use it in different formats.

we have said alpha channel is not really possible since there is lots of motion blur and refraction going on against the background. and some elements are entirely composed of multiple solid layers using blending modes to get transparency.

im tempted just to offer them the source frames and afx file.

[joconnell]

Yeah to be honest you'd be better off - it sounds like there's lots of things in there that need to be comped additively and ideally by someone who knows what they're doing - the clients thinking that they can put anything in as a background and it'll magically look perfect is a total non runner.

[fixeighted]

Hmm...not sure whether I understand completely what you have got to work with.

Are you saying that as a project you have a load of layers which work perfectly well against any background layer?
In which case can't you just turn the bkg off and render with the transparency?

Other than that, if you have a cut-down version of the file, showing at least partially what you need to achieve then I can take a look myself (I also have on-hand an AE genius who would know instantly if it's possible I think)

[super gnu]

Hmm...not sure whether I understand completely what you have got to work with.

Are you saying that as a project you have a load of layers which work perfectly well against any background layer?
In which case can't you just turn the bkg off and render with the transparency?

Other than that, if you have a cut-down version of the file, showing at least partially what you need to achieve then I can take a look myself (I also have on-hand an AE genius who would know instantly if it's possible I think)

thats what i thought, but for example if i turn bg off, the shadow layer (bw image set to multiply) shows up as white solid in the white areas, cos its got nothing to multiply against

the water droplets are layers without alpha, which use multimattes and reflection passes on "screen" and "overlay" to make them look nice (ish) . these also come out solid in the alpha when i export the comp in this way with alpha channel/transparency.

[joconnell]

For all your screen layers, you could use saturation to make them greyscale, then use set channel to put your luminance into the alpha channel for that layer - it'll mimic the amount that your layer was contributing.

[fixeighted]

I had a feeling my suggestion wouldn't be so simple a solution after I had another think about it. I forwarded this post to my friend who should be able to figure a way if one exists. I'll report back if so....fingers crossed.

Or maybe Joconnell's suggestion will do the trick somewhat - hope so.

[super gnu]

we have found a great "solution". we are biking a hard drive over to the agency with our aftereffects comp and all source frames.. they can do what they like with the background, and maybe they wont bug us for small tweaks either! sounds win-win to me.

-having said that id love to hear a proper solution that gives a reliable result without loads of fannying round.

[joconnell]

Good to hear SG - I'm travelling at the minute but I'll try and put together something as one way of doing it, it'll only be an approximation though and not a way to recreate what the renderer would have done (since we can't really do that in 2d)