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Render regions with alpha has white outline
Posted: Mon Feb 26, 2024 4:04 am
by timAugustine
Hi all,
My scene has a grassy foreground and some hills in the background. I'm rendering the grass separately with the alpha turned on. When I overlay the grassy layer on top of the mountains, I'm getting this weird white outline. Is there a setting I'm not aware of right now?
Render with the white outline

- Render
Here are the settings I'm using:

- Settings
Thanks in advance for any response!
Re: Render regions with alpha has white outline
Posted: Mon Feb 26, 2024 8:06 am
by Andreas_Resch
That seems to me an Premultiplied Alpha problem. I use an Alpha Convert node in the Compositor to fix that.
Re: Render regions with alpha has white outline
Posted: Mon Feb 26, 2024 8:59 am
by timAugustine
Thank you! I will try this tomorrow
Re: Render regions with alpha has white outline
Posted: Mon Feb 26, 2024 4:40 pm
by timAugustine
Hi,
Is this something from a version of blender without Octane? When I try to bring up the covert alpha node I keep getting errors with the word Octane all over it. Even after I select Cycles as the renderer. Is there a way to do this within octane settings?
Re: Render regions with alpha has white outline
Posted: Mon Feb 26, 2024 4:55 pm
by Andreas_Resch
Works in the custom build 28.9 Prime version.
Re: Render regions with alpha has white outline
Posted: Tue Feb 27, 2024 4:33 am
by timAugustine
I must have done something wrong. It works for me now. And it also fixed the issue for me. Thanks again!
Re: Render regions with alpha has white outline
Posted: Thu Mar 21, 2024 2:52 pm
by timAugustine
Hi, I have another question about this! Is it possible to set the output images to be premultipled directly in Octane? Just curious!
Thanks
Re: Render regions with alpha has white outline
Posted: Sun Mar 24, 2024 7:28 pm
by timAugustine
I didn't find it under blender export, but I did find it under the octane export subsection. It was available only for exr export options (not for png)
Re: Render regions with alpha has white outline
Posted: Mon Mar 25, 2024 5:08 am
by timAugustine
Once again, this website convinces me to do something better. Thanks!
I'm aware of some of the advantages of .exr usage but I've been hesitant to use them because I'm not very proficient with tools such as da vinci resolve.
Thanks again!
Re: Render regions with alpha has white outline
Posted: Mon Mar 25, 2024 5:02 pm
by timAugustine
Really loved fusion till I found it's 300 dollars, haha! I did look around and found that fusion 9 is free (for some reason I'm not complaining about). I'm not sure if it's any good as the current version is 18. I looked up Nuke and that's expensive as well.
I'll try to make it work with Fusion 9 and if not, I guess I'll try davinci. Are there any other software that you'll recommend?