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Normals don't show up inverted on meshes with negative tranformation
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Description

System Information
Operating system: Windows 10
Graphics card: NVIDIA GeForce GTX 970

Blender Version
Broken: 2.80, hash: c 93592109138, master, 2019-05-24

Short description of error
If an object with outward facing normals is scaled by a negative factor, the normal direction gets inverted.
This is however not shown in blender, since these objects still show up with outwards facing normals, once they are exported into a external application they show up as inverted.

Exact steps for others to reproduce the error
Enable face orientation under viewport overlays settings
Dublicate or link the default cube
Scale dublicate/link by a negative factor

Expected behaviour:
The scaled cube shows up red because of it's inward facing normals.

Actual behaviour:
The scaled cube still shows up blue as if it's normals were facing outwards.

Details

Type
Bug

Event Timeline

Daniel Bystedt (dbystedt) triaged this task as Confirmed, Medium priority.

I get the same results

System Information
Operating system: Windows-10-10.0.17763 64 Bits
Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 419.67

Blender Version
Broken: version: 2.80 (sub 73), branch: blender2.7, commit date: 2019-05-30 17:34, hash: rB846056de6b27
Worked: (optional)

Brecht Van Lommel (brecht) raised the priority of this task from Confirmed, Medium to Needs Triage by Developer.May 31 2019, 12:54 AM
Brecht Van Lommel (brecht) triaged this task as Needs Information from User priority.

Blender will automatically compensate for objects with negative scale, so that mirroring an object by giving it a negative scale works. That means that as far as Blender/Eevee/Cycles is concerned, the normal is in fact facing outward and indicating otherwise to the user would lead to the wrong normals for those renderers.

Arguably the bug is in the exporter which does not follow Blender's correction, but the bug report does not mention which exporter was used.

Brecht Van Lommel (brecht) claimed this task.

Closing due to lack of information to investigate the issue, we can reopen the report if more information is provided.