Author Topic: alpha channel boundaries are wite  (Read 3656 times)

2019-02-07, 12:04:14

artbox

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Hi everyone!

I have some issue with alpha channel. After I cutout the background i get white outline around my trees. Is it possible to fix this problem?


2019-02-07, 12:24:04
Reply #1

Beanzvision

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Hi there, What's your process of cutting them out? Are you using Photoshop? There are ways to fix this but knowing how it was done would fine tune my answer. Thanks

For now, you could review this:
https://coronarenderer.freshdesk.com/support/solutions/articles/5000653557-objects-with-opacity-maps-are-becoming-gray-when-they-are-far-away-from-camera-
Bengamin Jerrems:
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2019-02-07, 12:44:36
Reply #2

artbox

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 I just copy paste the alpha channel in to the layer mask, that's all. Also, I tried to adjust alpha image with levels or curves, but after that it looks worst. Even if I import png image without background in to the photoshop, I get the same result. It looks like tree leaves reflects bright color from the sky and the alpha channel cuts the object boundaries but doesn't  evaluate its burnout edges.

2019-02-07, 13:34:56
Reply #3

Beanzvision

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Photoshop kinda sucks when it comes to alpha. My first approach would be using the defringe setting in Photoshop to clean up the edges. If you want, I'm more than happy to look at your file. We have a private uploader that is linked in my signature below. ;)
Bengamin Jerrems:
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2019-02-07, 14:34:05
Reply #4

sebastian___

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Seems like exactly the things I was talking about in this post:
https://forum.corona-renderer.com/index.php?topic=18488.msg115961#msg115961
and here
https://forum.corona-renderer.com/index.php?topic=18488.msg115973#msg115973

And it seems no one knows or uses the solution with tga pre-multiplied which fixes the white outlines.

(but not sure if the trick with "pre-multiplied" would work in Photoshop, or just in after effects)