Zero Area Faces detected as Non Manifold Edges #1

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opened 2024-07-01 22:26:39 +02:00 by Cedric Steiert · 3 comments

blender 4.2 beta
addon version 1.0.0

As the original report got closed i checked and the described issue still seems relevant.

According to https://docs.blender.org/manual/en/4.1/addons/import_export/paper_model.html#usage the attached example should be detected as Zero Area Face.

There are a few kinds of topology that are possible in Blender but not in paper reality:
- N-gon faces (everything except triangles) that are not perfectly flat.
- Zero-length edges (two vertices exactly in the same spot and connected by an edge)
- Zero-area faces (typically their vertices lie all in line)

grafik

None Manifold edges on the other hand are usually when an edge is shared by more than two faces.

Original report: blender/blender-addons#104715

blender 4.2 beta addon version 1.0.0 As the original report got closed i checked and the described issue still seems relevant. According to https://docs.blender.org/manual/en/4.1/addons/import_export/paper_model.html#usage the attached example should be detected as Zero Area Face. > There are a few kinds of topology that are possible in Blender but not in paper reality: - N-gon faces (everything except triangles) that are not perfectly flat. - Zero-length edges (two vertices exactly in the same spot and connected by an edge) - Zero-area faces (typically their vertices lie all in line) ![grafik](/attachments/8f22cd20-bdc0-4576-880b-f4497db91965) None Manifold edges on the other hand are usually when an edge is shared by more than two faces. Original report: https://projects.blender.org/blender/blender-addons/issues/104715
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Hi!

The objects in your file don't seem to have any faces. So there are no faces to be marked as zero area faces.

Moreover, to be manifold, an edge has to be part of exactly two faces. An edge that is part of just a single face is therefore non manifold, and so is an edge with no face at all. Since the marked object on your example has no faces and five edges, all edges are non manifold and there is no zero area face, and so the check output seems correct.

Hi! The objects in your file don't seem to have any faces. So there are no faces to be marked as zero area faces. Moreover, to be manifold, an edge has to be part of _exactly_ two faces. An edge that is part of just a single face is therefore non manifold, and so is an edge with no face at all. Since the marked object on your example has no faces and five edges, all edges are non manifold and there is no zero area face, and so the check output seems correct.
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Ah ok, thank you for the explanation, was a misunderstanding from m side, as the original report only had a screenshot attached. Indeed when creating a face it gets detected as zero area face and as non-manifold edge. Then i'll consider this as resolved...

Ah ok, thank you for the explanation, was a misunderstanding from m side, as the original report only had a screenshot attached. Indeed when creating a face it gets detected as zero area face and as non-manifold edge. Then i'll consider this as resolved...
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Reference: extensions/print3d_toolbox#1
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