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Shading or Lighting Discrepancy issue
Confirmed, NormalPublicBUG

Description

System Information
Operating system: Windows-10-10.0.17763 64 Bits
Graphics card: GeForce RTX 2080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 440.97

Blender Version
Broken: version: 2.80 (sub 75), branch: master, commit date: 2019-07-29 14:47, hash: rBf6cb5f54494e
Worked: (optional)

Short description of error
So I’ve been having this problem since working in 2.8 and I don’t have a clue what could be causing this issue but I went and stripped down a project as simple as possible trying to isolate the root cause. It seems its a mesh that has an emissive material and when I disconnect the node or hide the mesh the problem disappears. Weird thing is that the brighter version is when hiding mesh number 2. I am attaching the file.

You will see how the tone changes. This never happened to me after so many years using Blender until now already in a few projects in 2.8.

Exact steps for others to reproduce the error

  1. Open attached file.
  2. Render once using slot 1.
  3. Hide mesh 2 or disconnect the emissive node.
  4. Render again using slot 2.
  5. Toggle with J

Notice the different lighting between each result.

Event Timeline

I can confirm that it renders darker with emissive object on.
However, there's a very complex World node setup in that scene:


I don't know what its purpose is, but with a simplified world background problem seems to go away.

That world setup comes from the Asset Management addon. If that could be the root cause then it would be great to know why that emissive mesh gets in conflict with it. It doesn't really make much sense even if you have wrong connections.

Richard Antalik (ISS) changed the task status from Needs Triage to Needs Information from User.Jan 15 2020, 5:46 PM

Is this still an issue with latest build? https://builder.blender.org/download/

I have just downloaded the project and latest beta build and still happening. What a mystery and super annoying not being able to use the addon because of that.

Philipp Oeser (lichtwerk) changed the task status from Needs Information from User to Needs Triage.Jan 15 2020, 6:50 PM

If the problem is word node setup, it would be nice to simplify it to make it easier for developers to investigate.
Given the seriousness of the problem, I don't think it's worth spending a lot of time trying to find the cause.

If the problem is word node setup, it would be nice to simplify it to make it easier for developers to investigate.
Given the seriousness of the problem, I don't think it's worth spending a lot of time trying to find the cause.

It might be a little bit more complex than the regular world setup but it is not complex at all for any developer. They also need it as is in order to find out the reason. If you make it less complex you might end up getting rid of the bug. I didn't have the time to try and find out what does exactly break it but I might try later today to narrow down even more the root cause.

Ok I spent some time to simplify that and the problem seems to be using Is Glossy Ray in the Mix Shader for the 2 HDRI nodes. A new simplified version has been uploaded. So the emissive light gets in conflict with that somehow. Is Camera ray does not have the same problem.

Germano Cavalcante (mano-wii) changed the task status from Needs Triage to Confirmed.Jan 16 2020, 5:45 PM
Germano Cavalcante (mano-wii) updated the task description. (Show Details)
Germano Cavalcante (mano-wii) changed the subtype of this task from "Report" to "Bug".

I have attached an even simpler file in the description.

This is most likely the same problem as this one: T73328
If you change "Sampling" from "Path Tracing" to "Branched Path Tracing" it renders correctly. It also renders correctly if "Multiple Importance" in the emissive shader is checked off.

That's a good guess. Thanks for sharing.