Maniphest T67907

Unwanted light reflections in EEVEE on surfaces facing away from light
Closed, Archived
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Assigned To
Clément Foucault (fclem)
Authored By
Daniel Bystedt (dbystedt)
Jul 29 2019, 10:56 PM
Tags
  • BF Blender
Subscribers
Clément Foucault (fclem)
Daniel Bystedt (dbystedt)
Philipp Oeser (lichtwerk)
Sebastian Parborg (zeddb)

Description

System Information
Operating system: Windows-10-10.0.17763 64 Bits
Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 430.86

Blender Version
Broken: version: 2.80 (sub 75), branch: master, commit date: 2019-07-28 15:07, hash: rBa49838ccb0f6
Worked: (optional)

Short description of error
[Please fill out a short description of the error here]
I was fiddling around in EEVEE with my tree creature file when I noticed a lot of noisy reflections on surfaces pointing away from the light source. After setting up a simple, diagnostic scene I discovered that surfaces facing away from the light source had an unwanted reflection of the light.

I don't understand how I haven't seen this before. The oldest build of 2.8 I have is from december 2018 and the results are the same when opening the file in that build as well.

Exact steps for others to reproduce the error
[Please describe the exact steps needed to reproduce the issue]
[Based on the default startup or an attached .blend file (as simple as possible)]

  1. turn on EEVEE and viewport shading
  2. make background black (to avoid distracting reflections from environment)
  3. create a sun light ( strength = 10, angle = 10 for more visible artefacts)
  4. create a sphere with the following material settings (base color = black, roughness = 0)
  5. observe the unwanted reflection on the surface facing away from the light source (this setup can be seen in attached .blend)

reflection_on_faces_with_opposite_normals_v001.blend782 KBDownload

Related Objects

Event Timeline

Daniel Bystedt (dbystedt) created this task.Jul 29 2019, 10:56 PM
Philipp Oeser (lichtwerk) assigned this task to Clément Foucault (fclem).Jul 30 2019, 10:50 AM
Philipp Oeser (lichtwerk) lowered the priority of this task from 90 to 80.
Philipp Oeser (lichtwerk) added subscribers: Clément Foucault (fclem), Philipp Oeser (lichtwerk).

I think this is the same as T66748 (possibly others, I recall this has been reported a couple of times)

So this might not be a bug, just to understand what is happening: may I ask @Clément Foucault (fclem) for some paper/clarification where this/our method gets described (including the limitation)? Would be good to know the reasoning behind this "tradeoff"...
Thx in advance!

Philipp Oeser (lichtwerk) added a subscriber: Sebastian Parborg (zeddb).Jul 30 2019, 10:51 AM

CC @Sebastian Parborg (zeddb)

Clément Foucault (fclem) added a comment.Jul 30 2019, 12:39 PM

This is a limitation/artifact of the area lighting. UE4 and Unity also have the same issue. The thing is, they have more robust shadowing and thoses artifacts are most of the time fixed by correct shadowing. The best you can do is to make your shadow sharper with less light bleeding.

Philipp Oeser (lichtwerk) added a comment.Jul 30 2019, 1:09 PM

@Clément Foucault (fclem): thx for clarifying.
So seems like this is unavoidable with sun lights (even with Shadow Softness set to 0.0, and a high Exponent) unless you drastically increase the angle.

This is a limitation/artifact of the area lighting

@Clément Foucault (fclem): this is limitied to sun lights only, right? (other light types dont seem to suffer from this -- at least not in my limited tests... just trying to forward the best information to users if this comes up again...)

Oh, btw. should we close this then as a known limitation?

Daniel Bystedt (dbystedt) added a comment.Jul 30 2019, 2:11 PM

Thanks for the quick response! The trick with the shadow settings you mentioned sounds really helpful.

I'll try that out in the future. All the best to you guys

Cheers
Daniel

Clément Foucault (fclem) changed the task status from Unknown Status to Archived.Jul 31 2019, 12:40 PM

just trying to forward the best information to users if this comes up again

https://blenderartists.org/t/unreal-rect-light-vs-eevee-area-light/1151377/5

this is limitied to sun lights only, right?

No, this is affecting all lamp types. It's just that sun lights have more shadowing issues.

Oh, btw. should we close this then as a known limitation?

Yes closing.