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Maniphest T45101

Hard edges don't go away when removed despite disappearance of cyan lines
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Description

System Information
Happens on both Windows 10 and Windows 7

Blender Version
2.74 000dfc0

Short description of error

Exact steps for others to reproduce the error
I imported an FBX file that came from Maya which worked fine aside from one small part of it. A certain small piece from the full model contained a part with anomalous shading where I am unable to bridge a flat face and make it appear flat.


After recalculating normals, making the whole mesh have flat shading, and removing edge shading (i.e. setting the mesh to smooth edges) it still occurs. No matter how I try to connect the front face (on both sides, including the one that isn't connected) either with n-gons, quads, or trianges, weird shading occurs.

I then exported this part of the model to an OBJ file,

anomaly.obj14 KBDownload
. Interestingly, when imported into Blender, this OBJ file contains hard edges that weren't in the model I exported.

After again removing the hard edges and setting the whole model to flat shading, the issue still persists like in the first image in this report. This means it's not an issue with the FBX importer because the anomaly is also contained in the OBJ file, or more likely, Blender's handling of it. Now, the model from this OBJ file can be exported to yet another OBJ file and it also contains the hard edges like in the second image in this report.

The issue can be fixed by clicking *Clear Custom Split Normals Data* under *Geometry Data* in the *Data* tab (the one with the triangle icon).

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Event Timeline

Keavon Chambers (keavon) created this task.Jun 17 2015, 8:00 PM
Keavon Chambers (keavon) raised the priority of this task from to 90.
Keavon Chambers (keavon) updated the task description. (Show Details)
Keavon Chambers (keavon) added a project: BF Blender.
Keavon Chambers (keavon) edited a custom field.
Keavon Chambers (keavon) added a subscriber: Keavon Chambers (keavon).
Bastien Montagne (mont29) changed the task status from Unknown Status to Unknown Status.Jun 17 2015, 10:02 PM
Bastien Montagne (mont29) claimed this task.
Bastien Montagne (mont29) added a subscriber: Bastien Montagne (mont29).

Well, thanks for the report, but you found the solution yourself - you have to clear custom normals data!

Ideally, clearing sharp edges should recompute/update clnors, but this is true for virtually any operation in Edit mode that affects topology and/or shading. Currently, this is not considered a bug but a known limitation and TODO. Custom normals are therefore only considered working for 'final' mesh, and should be cleared/updated manually in case you edit it.

Keavon Chambers (keavon) added a comment.EditedJun 17 2015, 10:29 PM

Thanks for taking a look and thanks for the info on that. However, as a user who doesn't know what all of those technical details mean, the way Blender acts in this edge case is clearly the behavior of a bug, not merely a limitation, so it seems to me that it should be classified as that. If I remove a hard edge, it should either work or tell me it didn't work due to a limitation. If it appears to work, but secretly it doesn't, that's a bug in my book.