OpenGL render with smoke and fire incorrect when using transparency #47639

New Issue

Miika Puustinen (miikap) · 2016-03-01T10:20:51+01:00

Miika Puustinen (miikap) commented

2016-03-01 10:20:51 +01:00

Operating system and graphics card
Windows 8.1
I7-5820K 3.3GHz, 2x Asus GTX 960 4Gb, 32Gb RAM

Blender Version
Broken: 2.77 RC1 b594b25
Worked: 2.76 official

Short description of error
If fire rate is more than 1, fire doesn't render properly with opengl render.

How to reproduce:

Select default cube
Make quick efffect: quick smoke (fire option)
Change fire rate from the emitter to 10
Tick of smoke high resolution from domain settings (to get faster preview)
Make domain bigger by turning on adaptive domain and changing additional to 32 for example
sim/playback to frame 50
render opengl render / viewport render
compare to viewport

Example file:
http://www.pasteall.org/blend/40879

Miika P

Operating system and graphics card Windows 8.1 I7-5820K 3.3GHz, 2x Asus GTX 960 4Gb, 32Gb RAM **Blender Version** Broken: 2.77 RC1 b594b25 Worked: 2.76 official **Short description of error** If fire rate is more than 1, fire doesn't render properly with opengl render. How to reproduce: - Select default cube - Make quick efffect: quick smoke (fire option) - Change fire rate from the emitter to 10 - Tick of smoke high resolution from domain settings (to get faster preview) - Make domain bigger by turning on adaptive domain and changing additional to 32 for example - sim/playback to frame 50 - render opengl render / viewport render - compare to viewport Example file: http://www.pasteall.org/blend/40879 - Miika P

Miika Puustinen (miikap) commented

2016-03-01 10:20:51 +01:00

Changed status to: 'Open'

Miika Puustinen (miikap) commented

2016-03-01 10:20:51 +01:00

Added subscriber: @MiikaPuustinen

Sergey Sharybin commented

2016-03-01 13:06:31 +01:00

Added subscriber: @Sergey

Sergey Sharybin commented

2016-03-01 13:06:31 +01:00

I can't really reproduce the issue, but i'm on Linux. Some things which could clarify situation for us:

What are exact steps of reproducing the issue with attached .blend file?
Is it viewport only problem, or render also differs from 2.76 to 2.77?
Please attach screenshoot of your problem.

I can't really reproduce the issue, but i'm on Linux. Some things which could clarify situation for us: - What are exact steps of reproducing the issue with attached .blend file? - Is it viewport only problem, or render also differs from 2.76 to 2.77? - Please attach screenshoot of your problem.

Miika Puustinen (miikap) commented

2016-03-01 14:13:52 +01:00

Without the file follow the steps.
With attatched .blend file just sim to frame where there is lot of flames (50 or so). Take an opengl render.

2.76 gives same result in opengl render and in the viewport.
2.77 fire is transparent and weird colored. Higher the flame value, lower the opacity of the flame (see screenshot).
http://www.pasteall.org/pic/100012

- Without the file follow the steps. - With attatched .blend file just sim to frame where there is lot of flames (50 or so). Take an opengl render. 2.76 gives same result in opengl render and in the viewport. 2.77 fire is transparent and weird colored. Higher the flame value, lower the opacity of the flame (see screenshot). http://www.pasteall.org/pic/100012

Sergey Sharybin commented

2016-03-02 08:53:04 +01:00

Ah ok, got it now. Not sure why OpenGL will use transparent background now actually. Needs investigation.

Kevin, any ideas here?

Ah ok, got it now. Not sure why OpenGL will use transparent background now actually. Needs investigation. Kevin, any ideas here?

Mike Erwin commented

2016-03-03 19:38:16 +01:00

Added subscriber: @MikeErwin

Mike Erwin commented

2016-03-03 19:41:40 +01:00

Added subscriber: @kevindietrich

Mike Erwin commented

2016-03-03 19:41:40 +01:00

@kevindietrich This is your area, right?

Kévin Dietrich commented

2016-03-03 22:43:02 +01:00

I checked out the commit before my rewrite of the smoke drawing and rendering either the default scene or a smoke sim also resulted in a transparent background, so chances are this is not related to volume rendering (or not my fault). Rendering fire alone is apparently broken after my change, so that one is on me.

Kévin Dietrich commented

2016-03-03 22:43:41 +01:00

This comment was removed by @kevindietrich

*This comment was removed by @kevindietrich*

Aaron Carlisle commented

2016-03-05 03:04:35 +01:00

Added subscriber: @Blendify

Aaron Carlisle commented

2016-03-05 03:04:35 +01:00

This is not only true for smoke but anything will render transparent unless show world background is enable. This is different then 2.76b where it works correctly.

Aaron Carlisle changed title from ~~Smoke sim opengl render doesn't match to viewport drawing~~ to OpenGL render is transparent unless "show background" is enabled

2016-03-05 03:05:43 +01:00

Miika Puustinen (miikap) commented

2016-03-05 10:30:52 +01:00

I think title was mistakenly changed to "OpenGL render is transparent unless "show background" is enabled".

This was the problem:

http://www.pasteall.org/pic/100187

Bottom image 2.77RC, top one 2.76.

I think title was mistakenly changed to "OpenGL render is transparent unless "show background" is enabled". This was the problem: http://www.pasteall.org/pic/100187 Bottom image 2.77RC, top one 2.76.

Brecht Van Lommel changed title from ~~OpenGL render is transparent unless "show background" is enabled~~ to OpenGL render with smoke and fire incorrect when using transparency

2016-03-05 13:27:11 +01:00

Brecht Van Lommel commented

2016-03-05 14:01:47 +01:00

Added subscriber: @brecht

Brecht Van Lommel commented

2016-03-05 14:01:47 +01:00

The shaders here changed a lot, previously it was drawing smoke and fire separately, with different OpenGL blend modes.

The tricky thing here is that we are rendering to a 0..1 clamped sRGB buffer with unpremultiplied alpha, where the correct thing to do would be to render to an unclamped linear premultiplied alpha buffer. Then you would just make fire purely emissive without affecting the alpha channel at all, but that doesn't work here.

The alpha channel in 2.76 is much too dense but perhaps that is required to make it work. I'm not sure yet what the solution is, maybe the shader needs to be split up again.

The shaders here changed a lot, previously it was drawing smoke and fire separately, with different OpenGL blend modes. The tricky thing here is that we are rendering to a 0..1 clamped sRGB buffer with unpremultiplied alpha, where the correct thing to do would be to render to an unclamped linear premultiplied alpha buffer. Then you would just make fire purely emissive without affecting the alpha channel at all, but that doesn't work here. The alpha channel in 2.76 is much too dense but perhaps that is required to make it work. I'm not sure yet what the solution is, maybe the shader needs to be split up again.

Kévin Dietrich was assigned by Sergey Sharybin

2016-07-27 11:27:46 +02:00

Sergey Sharybin commented

2016-07-27 11:27:46 +02:00

Kevin, did you have chance to have a look into fire issue?