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Material Preview blurred if Clearcoat is >0 in PBSDF shader
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System Information
Operating system: MacOS X 10.14
Graphics card: intel HD Graphics 4000

Blender Version
Worked: 2.80 Beta, 46ac288a9306, 2019-02-08 4:22, Branch: blender2.7

Short description of error
Material preview in Shading view shows distorted image if Principled BSDF node has Clearcoat parameter set greater than zero.

Exact steps for others to reproduce the error
. Create new generic scene with cube.
. Go to Shading view
. Select 'Principled BSDF' as Surface as material
. Open the Preview field if not already open
. Adjust Clearcoat param of PBSDF node in nodes pane.

Preview shredders

. Set back Clearcoat param to zero (0)

Preview ok



Event Timeline

Yes, easily.
Just start Blender 2.80 Beta anew, choose 'New File | General'
Go to Shading pane
Select Material Menu on the right
Drop open the Preview field
Enter any value >0 for Clearcoat parameter.
-> Preview image distorts.

This doesn't happen for me, so I'm guessing this might be a Mac problem. That is why I asked an other mac user to confirm if this happens for them too.

Added testing:
Metallic must be < 1, if Metallic is set to 1, effect vanishes.
Also, if I add any texture to roughness Material Preview window is correct.

Cannot reproduce here. It could be a driver bug for a specific GPU.

@William Reynish (billreynish) Ok, thanks for looking into this :)

@Nico Hartmann (DeNitz), can you attach (as a file) the output if you run blender with --debug-gpu and make the preview error appear?

You can additionally see if --debug-gpu-force-workarounds fixes anything.

My machine is a mid 2011 mac, and while I don't get that,
I get this: (for 0 clearcoat or otherwise, same)

@Joel Godin (FloridaJo) Not a bug. material preview just isn't supported properly for Eevee yet. See here for more: T57683

Sebastian Parborg (zeddb) lowered the priority of this task from Needs Triage by Developer to Needs Information from User.Feb 11 2019, 3:05 PM
Jacques Lucke (JacquesLucke) claimed this task.

More than a week without reply or activity. Due to the policy of the tracker archiving for until required info/data are provided.