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Problem Compositing Layers With Matched-framed Feathered Masks

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David Lawrence
Problem Compositing Layers With Matched-framed Feathered Masks
on Oct 21, 2015 at 6:17:29 am

Hi All,

I'm developing a dynamic linked workflow between Premiere Pro and After Effects for very simple composite images. I've run into a problem in AE compositing match-framed objects with feathered masks. AE is compositing differently than Premiere, creating a strange halo artifact.

It's easiest to show so here's an example:



The top is a Premiere timeline. Video track 1 is a black solid, track 2 above is a blue solid with a feathered mask of a square. A white duplicate with the same square mask dissolves in.

In Premiere, the dissolve is perfectly smooth, gradually transitioning the square from blue to white.

The bottom is the dynamic linked AE comp of the Premiere timeline above. To match the dissolve, opacity keyframes are set on the top blue layer to fade it out, over the middle white layer.

Note the white halo on the feather edges which pops on at the first frame of overlap. At this frame, all layers are at 100% opacity. Above is the exact same frame rendered in Premiere. This is what it's supposed to look like.

I've tried everything I can think of and I can't get AE to do simple smooth dissolves like in Premiere. What's going on and what am I doing wrong here? I'm completely baffled.

Many thanks in advance!

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David Lawrence
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Kalle Kannisto
Re: Problem Compositing Layers With Matched-framed Feathered Masks
on Oct 21, 2015 at 7:08:53 am

To cross fade, the white layer should go from 0 to 100 percent as the blue layer goes from 100 to 0.


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David Lawrence
Re: Problem Compositing Layers With Matched-framed Feathered Masks
on Oct 21, 2015 at 7:24:05 am
Last Edited By David Lawrence on Oct 21, 2015 at 7:31:01 am

[Kalle Kannisto] "To cross fade, the white layer should go from 0 to 100 percent as the blue layer goes from 100 to 0."

I tried that but it doesn't work.

It gets rid of the halo, but it's not a correct crossfade. As both layers reach the 50% opacity point, the square briefly darkens, i.e. in the middle of the transition, the top and middle layer both become transparent to the black layer for a brief moment.

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David Lawrence
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Kalle Kannisto
Re: Problem Compositing Layers With Matched-framed Feathered Masks
on Oct 21, 2015 at 7:38:51 am

Got you. To do this properly you'll have to use a feathered track matte for a precomp that changes from blue to white. This means, you'll make your blue and white (non-feathered) layers larger than the feathered area and animate the fade, precomp the two layers, then use another black and white feathered layer of the correct size as a track matte to reveal the precomp.


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Walter Soyka
Re: Problem Compositing Layers With Matched-framed Feathered Masks
on Oct 21, 2015 at 9:17:58 am

A true cross dissolve, which is easy in a video application, is somewhat harder in a compositing application. You have to separate the alpha from the RGB, fade the alpha and RGB separately, then apply the alpha fade to the RGB fade. (When alpha is full-on for both, as in the case of unmasked, full-frame video, you can simply fade out one RGB layer; it's mathematically identical.)

In this case, there is no need to use a track matte; since it's all the same mask, you can simply mask a precomp of unmasked blue dissolving out to unmasked white.

Note, too, that Premiere defaults to compositing in linear color. To get the same results in Ae, you'll have to open your project settings and enable "Blend Colors Using 1.0 Gamma."

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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David Lawrence
Re: Problem Compositing Layers With Matched-framed Feathered Masks
on Oct 21, 2015 at 9:33:23 pm

Kalle and Walter, thank you for your replies!

[Walter Soyka] "In this case, there is no need to use a track matte; since it's all the same mask, you can simply mask a precomp of unmasked blue dissolving out to unmasked white."

Nailed it! Pre-comped unmasked blue and white layers with the opacity change on blue, then mask the pre-comp over the black bg. Works perfectly.

[Walter Soyka] "Note, too, that Premiere defaults to compositing in linear color. To get the same results in Ae, you'll have to open your project settings and enable "Blend Colors Using 1.0 Gamma.""

Yes, sometimes I turn the "Composite in Linear Color" setting in Pr off depending on what it does to transitions. But it makes sense these settings need to match.

[Walter Soyka] "A true cross dissolve, which is easy in a video application, is somewhat harder in a compositing application. You have to separate the alpha from the RGB, fade the alpha and RGB separately, then apply the alpha fade to the RGB fade. (When alpha is full-on for both, as in the case of unmasked, full-frame video, you can simply fade out one RGB layer; it's mathematically identical.)"

This makes total sense, thank you.

Dynamic link is great but I guess I'm doing something that pushes the boundaries between video and compositing that dynamic link doesn't cross. Figures. ;)

I know the AE development team has their hands full right now, but in the future, how hard to you think it might be to have a composite preference setting that would tell the AE render pipeline to act like Pr? I'm sure I'm not the only one who would find this kind for setting useful for dynamically linked comps. Worthwhile feature request?

It's too bad because Pr CC's masking tools get me 90% of what I need but the extra 10% is critical and can really only be done in AE.

I'll have to see how easy it is to integrate these AE extra steps. It might be fine, actually. Time to test with the real video!

Thanks again!

_______________________
David Lawrence
art~media~design~research
propaganda.com
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facebook.com/dlawrence
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Walter Soyka
Re: Problem Compositing Layers With Matched-framed Feathered Masks
on Oct 21, 2015 at 10:20:12 pm

[David Lawrence] "I know the AE development team has their hands full right now, but in the future, how hard to you think it might be to have a composite preference setting that would tell the AE render pipeline to act like Pr? I'm sure I'm not the only one who would find this kind for setting useful for dynamically linked comps. Worthwhile feature request?"

I am all for anything that makes Ae/Pr integration better. They are *this close* to a really kicking finishing system.

That said, I think the challenge you speak of is broader than the render pipeline. Ae does not have a real concept of a transition, probably because Ae does not have the concept of a track as a container for multiple clips. Without that construct, the idea of native (non-effect) transitions gets weird fast. What does a cross-dissolve look like on a layer-based system, UI-wise?

In Ae today, you can emulate a transition by modifying properties, or you can transition with an effect on one layer that takes a background input from another layer and mixes them. If the Ae architecture were to be modified [link] such that effects had access to other layers' post-render output instead of the pre-render input they have now, then the Premiere cross-fade could produced by an effect such as GenArts Sapphire S_Dissolve, though the UI would be quite different. (FYI, it can be handled by S_Dissolve today if you alter the render order by precomping the masked blue solid in one precomp and the masked white solid in another.)

To get back to your specific feature request: closely emulating Premiere here is not just a matter of a setting that changes the way compositing is calculated, because the render pipeline is already consistent with Premiere. If you set up your Premiere timeline without native cross-clip transitions -- blue & dissolve on V3, over white on V2, over black on V1 -- you'll get the same blending result you were seeing from Ae at the top of the thread. Plus, I think that telling Ae to treat opacity adjustments as A mixes matting RGB mixes would actually break every other compositing operation except cross-fades.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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David Lawrence
Re: Problem Compositing Layers With Matched-framed Feathered Masks
on Oct 21, 2015 at 10:47:36 pm

[Walter Soyka] "In Ae today, you can emulate a transition by modifying properties, or you can transition with an effect on one layer that takes a background input from another layer and mixes them. If the Ae architecture were to be modified [link] such that effects had access to other layers' post-render output instead of the pre-render input they have now, then the Premiere cross-fade could produced by an effect such as GenArts Sapphire S_Dissolve, though the UI would be quite different. (FYI, it can be handled by S_Dissolve today if you alter the render order by precomping the masked blue solid in one precomp and the masked white solid in another.)"

I think I'm starting to appreciate why people like nodal compositors ;) The ability to reconfigure render flow at will would be handy here.

I'm going to experiment with an effects dissolve and see if that translates better. One nice benefit of precomping the dissolving layers is that it collapses the AE layers into a single pre comp that mirrors the corresponding track in Pr. This makes things a bit more manageable to work with in AE.

Great post, Walter, I'm learning so much. Thanks again!

_______________________
David Lawrence
art~media~design~research
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facebook.com/dlawrence
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Walter Soyka
Re: Problem Compositing Layers With Matched-framed Feathered Masks
on Oct 21, 2015 at 11:32:17 pm

[David Lawrence] "I think I'm starting to appreciate why people like nodal compositors ;) The ability to reconfigure render flow at will would be handy here."

Yes, indeed. Order of operations really, really matters. But of course, once you start re-arranging elements in time in a nodal compositor, you'll go back to appreciating why people like layer compositors! This is one of the things I like best about Smoke/Flame -- you have both timeline compositing and nodal compositing available to you all the time.

Out of curiosity, what is the last 10% of the challenge that you can't cover in Premiere? Maybe someone here would have a suggestion, or maybe there's a good area for a feature request.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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David Lawrence
Re: Problem Compositing Layers With Matched-framed Feathered Masks
on Oct 21, 2015 at 11:47:14 pm

[Walter Soyka] "Out of curiosity, what is the last 10% of the challenge that you can't cover in Premiere? Maybe someone here would have a suggestion, or maybe there's a good area for a feature request."

Great question! I'll start another thread for that because it really deserves its own. It's actually two feature requests - one for Pr (which would eliminate the need to go into AE) and one for AE, which would eliminate the crazy workaround I currently do to get it to work! :) More soon!

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David Lawrence
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facebook.com/dlawrence
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David Lawrence
Re: Problem Compositing Layers With Matched-framed Feathered Masks
on Oct 27, 2015 at 2:25:12 am

[Walter Soyka] "Out of curiosity, what is the last 10% of the challenge that you can't cover in Premiere? Maybe someone here would have a suggestion, or maybe there's a good area for a feature request."


Hi Walter - See this thread for more: https://forums.creativecow.net/readpost/2/1067326

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David Lawrence
art~media~design~research
propaganda.com
publicmattersgroup.com
http://lnkd.in/Cfz92F
facebook.com/dlawrence
twitter.com/dhl
vimeo.com/dlawrence/albums


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