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Masks meeting edge line?

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Ocean Byrne
Masks meeting edge line?
on Feb 21, 2013 at 9:37:29 pm

I have a BG Layer that I want to split to two layers, some of it in front of the Content Layer, and most of it behind the Content.

So I drew a mask on the BG Layer around the parts I want in front, and then I duplicated that layer with it's mask, moved it behind the Content Layer, and inverted the mask.

This does what I want, but their is a thin line of antialiasing marking where my mask is.

How can I get rid of that?

I should point out that the BG Layer is at 50% transparency, so I cant just have the fg version of it overlap the bg version with out getting doubled up layers of transparency. Also my scene is significantly more complex than just these 2.5 layers that I have been talking about.

Thanks


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Vishesh Arora
Re: Masks meeting edge line?
on Feb 21, 2013 at 10:28:15 pm

Ocean

A screenshot would help to understand the problem. Since I don't think there is any problem with the method that you have used.

Vishesh Arora
3D and Motion Graphics Artist
Films Rajendra

Blog:
http://digieffects.wordpress.com

2011 3D Demo Reel:








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Ocean Byrne
Re: Masks meeting edge line?
on Feb 21, 2013 at 10:56:14 pm

Can you guess where my mask is?



Okay, it is admittedly subtly, but if you look you can clearly see an arch around the top right of the screen, where the exact same mask on two different layers meets.


I have actually managed to fix the issue in this case, by making my masks straight vertical and horizontal, but I could imagine scenarios where that would not be possible...


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Vishesh Arora
Re: Masks meeting edge line?
on Feb 21, 2013 at 11:31:47 pm

Ocean

I can see the arc created by the masks. Don't know what exactly created this issue. May be the initial position of mask has slipped a little by mistake. Try creating the same Masks again and check the results. Though glad that you solved the problem.

Vishesh Arora
3D and Motion Graphics Artist
Films Rajendra

Blog:
http://digieffects.wordpress.com

2011 3D Demo Reel:








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Stephan Walsch
Re: Masks meeting edge line?
on Feb 22, 2013 at 1:10:34 am

Try setting the upper masks blending mode to "alpha add" (at the bottom of the list).
This mode is for exactly these situations where you combine two layers with masked that are inverted copies of each other.
Cheers"
Stephan

-------
Freelance
Motion Graphics / Grading
Berlin - Germany


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Vishesh Arora
Re: Masks meeting edge line?
on Mar 1, 2013 at 5:23:57 am

Ocean

Glad that you solved the issue but just because of curiosity I found the answer of your question. The reason that you are a getting a thin edge where the two masks intersect each other is because of Opacity Addition formula used in AE. For ex - Two layers with 50% opacity gives you 75% opacity and not 100%.

In the same way TWO PIXELS of 50% opacity overlapping will not give you 100 % opaque results.

So a thin edge is visible where transparent pixels overlap.

Stephan has given you the right answer. Use Alpha Add mode for the Top mask and the seam will disappear. It will directly ADD the opacity rather than using the default AE algorithms.

Vishesh Arora
3D and Motion Graphics Artist
Films Rajendra

Blog:
http://digieffects.wordpress.com

2011 3D Demo Reel:








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