Volumes do not appear when transparent film is enabled #42755

New Issue

gandalf3 · 2014-11-29T07:41:30+01:00

gandalf3 commented

2014-11-29 07:41:30 +01:00

System Information
Archlinux

Blender Version
Broken: 2.72b (9e963ae)

Short description of error
Volumes do not appear in the final combined pass when transparent film is enabled and the image is rendered with F12. They do appear in the various other passes though (e.g. emit).
It works as expected in viewport render.

Unrelated: also, there is a strange firefly which is visible in camera view+viewport render regardless of the number of samples. As the object is only rendered with an emission shader, this doesn't seem right..

Exact steps for others to reproduce the error

Open volume_and_transparent_film.blend
Enable viewport render (Shift Z). Works as expected
Press F12. Volume is not visible.

**System Information** Archlinux **Blender Version** Broken: 2.72b (9e963ae) **Short description of error** Volumes do not appear in the final combined pass when transparent film is enabled and the image is rendered with F12. They do appear in the various other passes though (e.g. emit). It works as expected in viewport render. *Unrelated: also, there is a strange firefly which is visible in camera view+viewport render regardless of the number of samples. As the object is only rendered with an emission shader, this doesn't seem right..* ![examp369.png](https://archive.blender.org/developer/F127669/examp369.png) **Exact steps for others to reproduce the error** 1. Open [volume_and_transparent_film.blend](https://archive.blender.org/developer/F127668/volume_and_transparent_film.blend) 2. Enable viewport render (Shift Z). Works as expected 2. Press F12. Volume is not visible.

gandalf3 commented

2014-11-29 07:41:30 +01:00

Changed status to: 'Open'

gandalf3 commented

2014-11-29 07:41:30 +01:00

Added subscriber: @gandalf3

Sergey Sharybin was assigned by Bastien Montagne

2014-11-30 14:51:33 +01:00

Bastien Montagne commented

2014-11-30 14:51:33 +01:00

Added subscriber: @mont29

Bastien Montagne commented

2014-11-30 14:51:33 +01:00

IIrc, this is expected result (a matter of premultiplied vs straight alpha…). Sergey should know for sure! :)

Sergey Sharybin commented

2014-12-02 10:12:15 +01:00

Changed status from 'Open' to: 'Archived'

Sergey Sharybin closed this issue

2014-12-02 10:12:15 +01:00

Sergey Sharybin commented

2014-12-02 10:12:15 +01:00

Yes, this is exactly a difference in handling premultiplied alpha in the viewport and image editor. This is a known behavior which i'm trying to address for 2.73 release. It's a bit tricky tho, because in viewport image is for sure properly premultiplied, without any possible precision issues caused by compositor, which make it really easy to mess things up in the image editor.

Anyway, there are some more changes to be done to the way how the alpha is handled in the image editor, would address them all together.

Yes, this is exactly a difference in handling premultiplied alpha in the viewport and image editor. This is a known behavior which i'm trying to address for 2.73 release. It's a bit tricky tho, because in viewport image is for sure properly premultiplied, without any possible precision issues caused by compositor, which make it really easy to mess things up in the image editor. Anyway, there are some more changes to be done to the way how the alpha is handled in the image editor, would address them all together.

Reginald Baxlore commented

2015-06-11 12:42:55 +02:00

Added subscriber: @blackdot

Reginald Baxlore commented

2015-06-11 12:42:55 +02:00

hi. has this issue been resolved, or can it be worked around somehow? i stumbled upon it today and found this report by websearching the problem. i'm using 2.74 (also tried the latest build for today). left is viewport rendered, and right f12 rendered. although the volumes (in my case those cylinders) can bee seen in various passes, they dont seem to be recognized by the "alpha". regards

hi. has this issue been resolved, or can it be worked around somehow? i stumbled upon it today and found this report by websearching the problem. i'm using 2.74 (also tried the latest build for today). left is viewport rendered, and right f12 rendered. ![alpha-volume-issue.png](https://archive.blender.org/developer/F189557/alpha-volume-issue.png) although the volumes (in my case those cylinders) can bee seen in various passes, they dont seem to be recognized by the "alpha". regards

Alex de Mulder commented

2015-07-07 22:00:56 +02:00

Added subscriber: @alexdemulder

Alex de Mulder commented

2015-07-07 22:00:56 +02:00

I'm still getting this bug in 2.75, I believe it was gone in 2.74 but I'd have to check. Should this be fixed? If so I'd happily share my scene.

gandalf3 commented

2015-07-07 23:29:10 +02:00

AFAIK this has yet to be fixed (if it was gone in 2.74, thats odd..), as it's caused by fundamental differences in alpha handling (as Sergey explained).

Delo Lat commented

2016-02-17 11:30:22 +01:00

Added subscriber: @edisto

Delo Lat commented

2016-02-17 11:30:22 +01:00

http://blender.stackexchange.com/questions/32900/how-to-properly-render-smoke-on-a-transparent-background
Attempt 1 works very good as a workaround.

http://blender.stackexchange.com/questions/32900/how-to-properly-render-smoke-on-a-transparent-background Attempt 1 works very good as a workaround.

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Volumes do not appear when transparent film is enabled #42755