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Maniphest T56343

2.8/2.79 Bug: Glare Effect in Compositing Not Working with Transparency in Cycles/Eevee
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Description

System Information
Windows 10 64-bit, Geforce GTX 970, Intel Core i7-6700k, 16GB Ram
Blender Version
2.80.0
Date: 2018-08-11 18:54
Hash: b4b8d3ab0e4
Branch: blender2.8

Short description of error
The Glare effect in Compositing does not work properly in both Cycles and Eevee when using transparency. This issue also exists in 2.79 versions.

Exact steps for others to reproduce the error
Select the render engine of choice, choose PNG for the output with alpha included, enable the Scene's transparency in Film, then render image.

lights.blend609 KBDownload

Related Objects

Event Timeline

Drew Sikes (DTStheTDS) created this task.Aug 13 2018, 4:37 AM
Bastien Montagne (mont29) assigned this task to Jeroen Bakker (jbakker).Aug 13 2018, 11:33 AM
Bastien Montagne (mont29) lowered the priority of this task from 90 to Normal.
Bastien Montagne (mont29) removed projects: Eevee, Cycles.
Bastien Montagne (mont29) added subscribers: Jeroen Bakker (jbakker), Bastien Montagne (mont29).

I guess that’s something to do with premultiplied/straight alpha, @Jeroen Bakker (jbakker) care to check? Thanks.

Drew Sikes (DTStheTDS) added a comment.Aug 13 2018, 12:36 PM

It might have something to do with it. This was pretty much the closest workaround solution I came up with, even then there's still some compromise. Is it a compositor/viewport problem or is this just normal for some effects in Blender? Sorry, I'm still fairly new to Blender.

Brecht Van Lommel (brecht) closed this task as a duplicate of T52680: Alpha difference Viewport/F12 .Aug 13 2018, 4:27 PM
Brecht Van Lommel (brecht) added a subscriber: Brecht Van Lommel (brecht).

The compositor actually works fine, but the image editor is not displaying it correctly, see T52680.

If you composite the result over another image or save as OpenEXR it should work fine.

Yevgeny Makarov (jenkm) added a subscriber: Yevgeny Makarov (jenkm).Aug 13 2018, 4:50 PM

@Brecht Van Lommel (brecht)

The problem lies elsewhere.

The render has zero alpha, outside the object.
After the Glare effect it remains zero.

That is, the Glare node does not take into account transparency.

Brecht Van Lommel (brecht) added a comment.Aug 13 2018, 5:08 PM

The fact that is has zero alpha outside the object is correct, it's intended to add glow without obscuring anything behind.

Philipp Oeser (lichtwerk) mentioned this in T72014: Glare Node Transparency Issue.Nov 29 2019, 11:33 AM
Philipp Oeser (lichtwerk) merged a task: T72014: Glare Node Transparency Issue.
Philipp Oeser (lichtwerk) added subscribers: Brenden Ketchum (Brelidav), Philipp Oeser (lichtwerk).