AMD GPU - EEVEE - Compositor is broken again in 2.93 (Regression) - Alpha Channel crazy behaviour is back. #88844

New Issue

Chris Bell · 2021-06-04T23:00:30+02:00

Chris Bell commented

2021-06-04 23:00:30 +02:00

System Information
Operating system: Windows 10 64bit
Graphics card: AMD Radeon RX580 with latest official drivers.

Blender Version
Broken: 2.93 (Official)
Worked: 2.92.0

Short description of error
Same reported here by myself .. that was broken in 2.91, then fixed (presumably.. the little compositing I did always worked) in 2.92.. and now broken again in 2.93. Now it doesn't crash to desktop, but the absolute random and unpredictable behavior/result with any operation on the alpha channels is absolutely the same described there.
https://developer.blender.org/T84163

Using EEVEE : compositing in the Compositor gives me totally unpredictable results (with Alpha Channels used absolutely in a random way) when combining two basic (even empty) scenes with 2 Renderlayers Input Nodes linked to a Color -> Mix or Color -> AlphaOver Node..

And when I say randomly.. I intend TOTALLY : sometimes (very rarely) alpha channel can be rightly taken into account, but most of the time it is not and (with the same node setup) you can get EVERY possible combination of the two RenderLayers, ... even a totally transparent image or (happend just yet) the renderlayer used both as Image AND alpha channel (make the compositing more transparent where it's dark and opaque where it's bright )..

Exact steps for others to reproduce the error
I provide a very basic and simple scene to test: there's only a holdout shader on a Scene1 object (cube this time) and some Material Nodes in world space to get a background on a Scene2 which is totally empty (but it's absolutely the same if you turn on the Film - Transparent render option on the first scene.. obviously the transparent part is inverted in this case.)

After the luck with 2.92 ... I'm getting (again) totally unpredictable result by any node using alpha channels .. with the two Render Layers composited absolutely at random in every possibile combination/way (even as a totally transparent image).Compositor_Is_Broken_Again.blend

**System Information** Operating system: Windows 10 64bit Graphics card: AMD Radeon RX580 with latest official drivers. **Blender Version** Broken: 2.93 (Official) Worked: 2.92.0 **Short description of error** Same reported here by myself .. that was broken in 2.91, then fixed (presumably.. the little compositing I did always worked) in 2.92.. and now broken again in 2.93. Now it doesn't crash to desktop, but the absolute random and unpredictable behavior/result with any operation on the alpha channels is absolutely the same described there. https://developer.blender.org/T84163 Using EEVEE : compositing in the Compositor gives me totally unpredictable results (with Alpha Channels used absolutely in a random way) when combining two basic (even empty) scenes with 2 Renderlayers Input Nodes linked to a Color -> Mix or Color -> AlphaOver Node.. And when I say randomly.. I intend TOTALLY : sometimes (very rarely) alpha channel can be rightly taken into account, but most of the time it is not and (with the same node setup) you can get EVERY possible combination of the two RenderLayers, ... even a totally transparent image or (happend just yet) the renderlayer used both as Image AND alpha channel (make the compositing more transparent where it's dark and opaque where it's bright ).. **Exact steps for others to reproduce the error** I provide a very basic and simple scene to test: there's only a holdout shader on a Scene1 object (cube this time) and some Material Nodes in world space to get a background on a Scene2 which is totally empty (but it's absolutely the same if you turn on the Film - Transparent render option on the first scene.. obviously the transparent part is inverted in this case.) After the luck with 2.92 ... I'm getting (again) totally unpredictable result by any node using alpha channels .. with the two Render Layers composited absolutely at random in every possibile combination/way (even as a totally transparent image).[Compositor_Is_Broken_Again.blend](https://archive.blender.org/developer/F10158339/Compositor_Is_Broken_Again.blend)

Chris Bell commented

2021-06-04 23:00:30 +02:00

Added subscriber: @Chris-Bell

Chris Bell changed title from ~~AMD GPU - EEVEE - Compositor is broken again in 2.93 (Regression) -~~ to AMD GPU - EEVEE - Compositor is broken again in 2.93 (Regression) - Alpha Channel crazy behaviour is back.

2021-06-04 23:01:22 +02:00

Chris Bell commented

2021-06-05 21:25:49 +02:00

An update on me investigating this.

the issue is present in Blender 2.92.0 too. I tried to render the same blend file multiple times.. and I got the same unpredictable results as with 2.93.
Maybe ( I need to do more testing on this) this mess with the alpha channels affects only the render view: I did a couple of brief rendering tests and the resulting video was rendered correctly.

An update on me investigating this. 1. the issue is present in Blender 2.92.0 too. I tried to render the same blend file multiple times.. and I got the same unpredictable results as with 2.93. 2. Maybe ( I need to do more testing on this) this mess with the alpha channels affects only the render view: I did a couple of brief rendering tests and the resulting video was rendered correctly.

Ankit Meel commented

2021-06-16 16:39:39 +02:00

Added subscriber: @ankitm

Ankit Meel commented

2021-06-16 16:39:39 +02:00

To observe the randomness, do we have to render the scene again, or change some compositor node parameters or something else ?

Ankit Meel commented

2021-06-22 22:41:08 +02:00

the issue is present in Blender 2.92.0 too. I tried to render the same blend file multiple times.. and I got the same unpredictable results as with 2.93.

Tried rendering multiple times in 2.92 and ce64cfd6ed the given file.

I get the above every time.

> the issue is present in Blender 2.92.0 too. I tried to render the same blend file multiple times.. and I got the same unpredictable results as with 2.93. Tried rendering multiple times in 2.92 and ce64cfd6edc2a0ec0aabfd4daaa5f655763cc74b the given file. ![image.png](https://archive.blender.org/developer/F10188456/image.png) I get the above every time.

Chris Bell commented

2021-07-13 04:09:43 +02:00

In #88844#1177718, @ankitm wrote:
To observe the randomness, do we have to render the scene again, or change some compositor node parameters or something else ?

No, I (still) have different results everytime I hit "render" without changing any parameter in the compositor (in EVERY project/render that uses compositor)..

What GPU do you have ? An old AMD card like mine ? (RX 580) ? I think this issue (as other ones) it's GPU/driver related.

Anyway.. while the render window displays this crazy random unpredictable (and for the most part TOTALLY WRONG) composited images.. the rendered image/video seems to be ok.. but that's still a huge problem, since you have to render a image/video EACH TIME to see the "true" aspect of your compositing, so the Blender render window is totally useless for previewing what you're doing,. and when a lot of composting in involved.. this is a very bad thing.

> In #88844#1177718, @ankitm wrote: > To observe the randomness, do we have to render the scene again, or change some compositor node parameters or something else ? No, I (still) have different results everytime I hit "render" without changing any parameter in the compositor (in EVERY project/render that uses compositor).. What GPU do you have ? An old AMD card like mine ? (RX 580) ? I think this issue (as other ones) it's GPU/driver related. Anyway.. while the render window displays this crazy random unpredictable (and for the most part TOTALLY WRONG) composited images.. the rendered image/video seems to be ok.. but that's still a huge problem, since you have to render a image/video EACH TIME to see the "true" aspect of your compositing, so the Blender render window is totally useless for previewing what you're doing,. and when a lot of composting in involved.. this is a very bad thing.

Omar Emara commented

2022-02-24 10:20:48 +01:00

Added subscriber: @OmarEmaraDev

Omar Emara commented

2022-02-24 10:20:48 +01:00

Changed status from 'Needs Triage' to: 'Needs User Info'

Omar Emara commented

2022-02-24 10:20:48 +01:00

I can't replicate the issue either.
When you say that the bad result "affects only the render view", do you mean the Composite result in the image editor after render? Or the backdrop in the compositor editor?
Can you provide a screenshot of the randomness you mentioned? Does that also happen for Cycles renders?

I can't replicate the issue either. When you say that the bad result "affects only the render view", do you mean the Composite result in the image editor after render? Or the backdrop in the compositor editor? Can you provide a screenshot of the randomness you mentioned? Does that also happen for Cycles renders?

Omar Emara commented

2022-05-25 11:20:09 +02:00

Just a poke regarding my inquiry above, otherwise we will have to archive this for now.

Chris Bell commented

2022-05-26 17:21:45 +02:00

In #88844#1364007, @OmarEmaraDev wrote:
Just a poke regarding my inquiry above, otherwise we will have to archive this for now.

Sorry for the late reply, I missed the notification of your message on February.. and in the meanwhile I didn't any more compositing test, I was into geometry nodes all the time.

For "Render View" i meant the Composite result in the Image Editor shown after the rendering, the backdrop in the compositor editor always showed the corrected compositing result, while in the image editor I always got a totally random result/combination (included the correct one very few times)

Tried now the same scene i posted here with Blender 3.1.2 and it seems to work fine with it now. I tried a 20-30 consecutive renderings and the Image Editor showed me the correct compositing result every time.
I was very curios at this point .. so I tested it in Blender 2.93.8 .. and I got the same random results as before, when I opened the thread.

Since I have exactly the same PC/GPU and also the same GPU Driver Version as before.. I suppose something in the Image Editor got fixed between 2.93 and 3.1.2..

So this report may be archived/closed; I will do some further compositing tests in EEVEE (using cryptomatte too) and if I get some weird results again I will open a new one, but for now everything seems to work as it should.

Thanks to everyone for the wonderful job you are doing with Blender and for the attention you always put into every bug report.

> In #88844#1364007, @OmarEmaraDev wrote: > Just a poke regarding my inquiry above, otherwise we will have to archive this for now. Sorry for the late reply, I missed the notification of your message on February.. and in the meanwhile I didn't any more compositing test, I was into geometry nodes all the time. For "Render View" i meant the Composite result in the Image Editor shown after the rendering, the backdrop in the compositor editor always showed the corrected compositing result, while in the image editor I always got a totally random result/combination (included the correct one very few times) Tried now the same scene i posted here with Blender 3.1.2 and it seems to work fine with it now. I tried a 20-30 consecutive renderings and the Image Editor showed me the correct compositing result every time. I was very curios at this point .. so I tested it in Blender 2.93.8 .. and I got the same random results as before, when I opened the thread. Since I have exactly the same PC/GPU and also the same GPU Driver Version as before.. I suppose something in the Image Editor got fixed between 2.93 and 3.1.2.. So this report may be archived/closed; I will do some further compositing tests in EEVEE (using cryptomatte too) and if I get some weird results again I will open a new one, but for now everything seems to work as it should. Thanks to everyone for the wonderful job you are doing with Blender and for the attention you always put into every bug report.

Omar Emara commented

2022-05-27 08:25:57 +02:00

Changed status from 'Needs User Info' to: 'Archived'

Omar Emara closed this issue

2022-05-27 08:25:57 +02:00

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AMD GPU - EEVEE - Compositor is broken again in 2.93 (Regression) - Alpha Channel crazy behaviour is back. #88844