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Stretched Shading On Metallic Low Roughness Surfaces In EEVEE
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Description

System Information
Operating system: Windows-10-10.0.17134 64 Bits
Graphics card: GeForce GTX 770/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.36

Blender Version
Broken: version: 2.80 (sub 74), branch: master, commit date: 2019-07-16 23:38, hash: rB4a5e046c923f

Short description of error
When using the 'metallic' and 'roughness' parameters of 'Principled Shader' EEVEE gives unexpected results with HDRI lighting. At 'Metallic=1.0' 'Roughness=0.25' while using HDRIHaven 'Studio_Small_01'-hdr clear streaking/stretching of light sources can be seen towards the middle point of the lights. This effect is most prominent when there are multiple bright, point like, light sources where the streaking seems to converge to the middle of the light sources while being barely noticeable with very soft light sources or single strong light source (such as sunset)

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)]
-Browse to hdrihaven.com
-Search for 'Studio Small 01' and 'Georgentor', download sizes you like (I've tested 2k, 8k and 16k)
-Open Blender, add subdivision modifier to default cube with 2 levels, apply
-Set Cube/Sphere to smooth shading, go to material settings set metallic 1.0 and roughness 0.0
-Go To world settings, Set surface to Background, color to Environment, select Studio Small 01.hdr
-Go to viewport render mode, view sphere from top view
-Increase roughness from 0.0 to 0.5
-Observe how very aggressive streaks appear to converge in the middle of the 3 light sources (especially between 0.17-0.5 range of roughness)

Notes: Similar effect can be seen in the Georgentor hdri but this time with strong light from 3 different doors. It should be noted that this issue is specific to using HDRI and does not occur when using no HDRI and 3 'Point Light' objects.
(This is my first bug report here I'm sorry if I ended up spamming. I noticed this issue couple months ago and tried originally to attract more professional opinion on it via social media/asking in forums but it never really got noticed. I've included link to comparison between same values in b3d and Substance Painter
https://drive.google.com/file/d/1U4fRsp177wPOTVNph1MbQuAkKcHJ9evX/view)

Details

Type
Bug

Event Timeline

T.R.O. Nunes (3Rton) updated the task description. (Show Details)
Sebastian Parborg (zeddb) closed this task as Archived.
Sebastian Parborg (zeddb) claimed this task.

This is a known limitation. You can increase filtering quality to get rid of it partially.

@Sebastian Parborg (zeddb) where I can read about this limitation and reasons of artifact?

@Vyacheslav (hitrpr) doesn't seem like it. You'd probably have to directly ask the EEVEE developer https://wiki.blender.org/wiki/Modules