EEVEE principled bsdf shader no longer handles negative specular values gracefully #87107

New Issue

Amir Shehata · 2021-04-01T05:43:52+02:00

Amir Shehata commented

2021-04-01 05:43:52 +02:00

System Information
Operating system: Linux-5.4.0-70-generic-x86_64-with-glibc2.31 64 Bits
Graphics card: GeForce GTX 1060 6GB/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 460.39

Blender Version
Broken: version: 2.93.0 Alpha, branch: master, commit date: 2021-03-31 04:29, hash: e7f890aa59
Worked: 2.92

Short description of error
Specular values less than 0 causes shader in EEVEE viewport to be black.. The same is not observed in cycles. Also tried blender 2.92 and it doesn't have this issue.

Exact steps for others to reproduce the error
Set Specular to a values less than 0 on the Principled shader in EEVEE 2.93
Note: SSR must be off in the Render Properties.
T87107specular.blend
2.93

2.92

One reason this is an issue is due to the RGB Curve node interpolating values below 0 when using the default auto handle, as shown in the original report images below.
see node setup below

If I disconnect the specular the texture looks fine

Blender 2.92 doesn't have the same problem

**System Information** Operating system: Linux-5.4.0-70-generic-x86_64-with-glibc2.31 64 Bits Graphics card: GeForce GTX 1060 6GB/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 460.39 **Blender Version** Broken: version: 2.93.0 Alpha, branch: master, commit date: 2021-03-31 04:29, hash: `e7f890aa59` Worked: 2.92 **Short description of error** Specular values less than 0 causes shader in EEVEE viewport to be black.. The same is not observed in cycles. Also tried blender 2.92 and it doesn't have this issue. **Exact steps for others to reproduce the error** Set Specular to a values less than 0 on the Principled shader in EEVEE 2.93 Note: SSR must be off in the Render Properties. [T87107specular.blend](https://archive.blender.org/developer/F9917174/T87107specular.blend) 2.93 ![2.93_specNegOne.jpg](https://archive.blender.org/developer/F9917178/2.93_specNegOne.jpg) 2.92 ![2.92_specNegOne.jpg](https://archive.blender.org/developer/F9917180/2.92_specNegOne.jpg) One reason this is an issue is due to the RGB Curve node interpolating values below 0 when using the default auto handle, as shown in the original report images below. see node setup below ![image.png](https://archive.blender.org/developer/F9916537/image.png) If I disconnect the specular the texture looks fine ![image.png](https://archive.blender.org/developer/F9916539/image.png) Blender 2.92 doesn't have the same problem ![image.png](https://archive.blender.org/developer/F9916542/image.png)

Amir Shehata commented

2021-04-01 05:43:52 +02:00

Added subscriber: @AmirShehata

Philipp Oeser commented

2021-04-01 11:58:06 +02:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2021-04-01 11:58:06 +02:00

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

Philipp Oeser commented

2021-04-01 11:58:06 +02:00

Please always attach a simple example .blend file (including packed textures) that demonstrates this issue.
(this ensures we are all on the same page and just speeds up the process if multiple devs are looking into this)

Please always attach a simple example .blend file (including packed textures) that demonstrates this issue. (this ensures we are all on the same page and just speeds up the process if multiple devs are looking into this)

Amir Shehata commented

2021-04-01 18:38:20 +02:00

Here is a simple blend file which shows the issue.
specular.blend
You can open the file in 2.93 and see the issue.
If you open it in 2.92 it looks fine.
In 2.93, if you disconnect the specular input of the principled shader, then the problem disappears (as far as I can see).

Here is a simple blend file which shows the issue. [specular.blend](https://archive.blender.org/developer/F9917043/specular.blend) You can open the file in 2.93 and see the issue. If you open it in 2.92 it looks fine. In 2.93, if you disconnect the specular input of the principled shader, then the problem disappears (as far as I can see).

Amir Shehata commented

2021-04-01 18:59:52 +02:00

I duplicated the texture and made the one that goes to the specular "non-color", that seemed to resolve the problem on 2.93.
This is a behavior difference between 2.92 and 2.93. Is that intended?

I duplicated the texture and made the one that goes to the specular "non-color", that seemed to resolve the problem on 2.93. This is a behavior difference between 2.92 and 2.93. Is that intended? ![image.png](https://archive.blender.org/developer/F9917065/image.png)

Evan Wilson commented

2021-04-01 20:44:10 +02:00

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

Evan Wilson commented

2021-04-01 21:50:55 +02:00

Added subscribers: @fclem, @EAW

Evan Wilson commented

2021-04-01 21:50:55 +02:00

Changed status from 'Needs Triage' to: 'Confirmed'

Evan Wilson commented

2021-04-01 21:50:55 +02:00

So the issue here is that RGB Curve node causes some of the values of the sRGB texture to go negative.

In 2.92, negative Specular values don't break the Principled BDSF

In 2.93, negative specular values do. Values <0 will make the output black. Values ⪅ -0.9 cause the shader to flicker between white and black using the slider, with white artifacts around the edge at -1.

I will confirm for now. However, I can't say that this is a bug, as I don't believe negative specular values are expected. If not, perhaps they should be clamped to zero?
@fclem recently did work a lot of work in the closure and reflections part of EEVEE's code. Before bisecting it to a specific commit, I will leave it up to him to decide if he considers this a bug.

So the issue here is that RGB Curve node causes some of the values of the sRGB texture to go negative. In 2.92, negative Specular values don't break the Principled BDSF ![2.92_specNegOne.jpg](https://archive.blender.org/developer/F9917151/2.92_specNegOne.jpg) In 2.93, negative specular values do. Values <0 will make the output black. Values ⪅ -0.9 cause the shader to flicker between white and black using the slider, with white artifacts around the edge at -1. ![2.93_specNegOne.jpg](https://archive.blender.org/developer/F9917154/2.93_specNegOne.jpg) I will confirm for now. However, I can't say that this is a bug, as I don't believe negative specular values are expected. If not, perhaps they should be clamped to zero? @fclem recently did work a lot of work in the closure and reflections part of EEVEE's code. Before bisecting it to a specific commit, I will leave it up to him to decide if he considers this a bug.

Evan Wilson changed title from ~~EEVEE principled bsdf shader specular is not working as expected~~ to EEVEE principled bsdf shader no longer handles negative specular values gracefully

2021-04-01 22:10:53 +02:00

Amir Shehata commented

2021-04-02 00:49:15 +02:00

Could this be related to: https://developer.blender.org/T86578
From @EAW description:
" Values <0 will make the output black. Values ⪅ -0.9 cause the shader to flicker between white and black using the slider, "
Could this result in the fireflies we see during the render?

Could this be related to: https://developer.blender.org/T86578 From @EAW description: " Values <0 will make the output black. Values ⪅ -0.9 cause the shader to flicker between white and black using the slider, " Could this result in the fireflies we see during the render?

Evan Wilson commented

2021-04-02 01:49:43 +02:00

@AmirShehata I don’t think so. The general area is similar but the issues appear to me to be different. #86578 has artifacts in both 2.92 and 2.93, while this report’s issue doesn’t appear in 2.92.

blender-admin commented

2021-04-08 17:43:23 +02:00

This issue was referenced by 08ae545de4

This issue was referenced by 08ae545de433272827d6b244020efe677cf3670e

Clément Foucault commented

2021-04-08 17:45:37 +02:00

Changed status from 'Confirmed' to: 'Resolved'

Clément Foucault closed this issue

2021-04-08 17:45:37 +02:00

Clément Foucault self-assigned this 2021-04-08 17:45:37 +02:00

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EEVEE principled bsdf shader no longer handles negative specular values gracefully #87107