bmesh.ops.subdivide_edges doesn't report all inner edges in 'geom_inner' #83926

New Issue

Stanislav Blinov · 2020-12-18T12:40:18+01:00

Stanislav Blinov commented

2020-12-18 12:40:18 +01:00

Blender Version
Broken: 2.91, 2.92 master
Worked: never?

Short description of error

I'm not sure if it's a bug or if there's some underlying reason for this behavior. The BMesh subdivide edges op returns three lists of geometry, one of which is 'geom_inner'. It appears that this list doesn't always contain all new 'inner' edges. This depends on the topology being passed to the op. Example image, created from the attached blend file:

On the left is the original selection of edges being passed in to the op, and on the right - selection of edges from the resulting 'geom_inner' list. As you can see, some of the edges aren't selected (i.e. they were not present in the list). We can work around this by iterating all vertices from 'geom_inner' list, and taking all edges linked to them that are not also part of the 'geom_split' list returned by the op, but it feels like this information should just be provided in the 'geom_inner' list.

Exact steps for others to reproduce the error
Load the attached file and run the script.

subdivide_geom_inner_issue.blend

**Blender Version** Broken: 2.91, 2.92 master Worked: never? **Short description of error** I'm not sure if it's a bug or if there's some underlying reason for this behavior. The [BMesh subdivide edges op ](https://docs.blender.org/api/current/bmesh.ops.html#bmesh.ops.subdivide_edges) returns three lists of geometry, one of which is 'geom_inner'. It appears that this list doesn't always contain all new 'inner' edges. This depends on the topology being passed to the op. Example image, created from the attached blend file: ![image.png](https://archive.blender.org/developer/F9516365/image.png) On the left is the original selection of edges being passed in to the op, and on the right - selection of edges from the resulting 'geom_inner' list. As you can see, some of the edges aren't selected (i.e. they were not present in the list). We can work around this by iterating all **vertices** from 'geom_inner' list, and taking all edges linked to them that are not also part of the 'geom_split' list returned by the op, but it feels like this information should just be provided in the 'geom_inner' list. **Exact steps for others to reproduce the error** Load the attached file and run the script. [subdivide_geom_inner_issue.blend](https://archive.blender.org/developer/F9516370/subdivide_geom_inner_issue.blend)

Stanislav Blinov commented

2020-12-18 12:40:18 +01:00

Added subscriber: @Stan_Pancakes

Philipp Oeser commented

2021-01-06 15:13:52 +01:00

Added subscribers: @ideasman42, @lichtwerk

Philipp Oeser commented

2021-01-06 15:13:52 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Philipp Oeser self-assigned this 2021-01-06 15:13:52 +01:00

Philipp Oeser commented

2021-01-06 15:13:52 +01:00

Checked on this and here are my findings:

the edges currently marked with geom_inner (the "working" ones) are from a special case in bmo_subdivide_edges_exec where no SubDPattern is available for the SubDFaceData
for the remaining cases where the pattern-based edge subdivider creates those "missing" edges edges are not flagged ELE_INNER
there are many different patterns, but afaict, the fundamental operation in all of them is connect_smallest_face, so easiest solution would be to flag new edges there
(or maybe this needs more flexibility in that one could pass in which flag to use? made optional entirely?)

Will post a Diff shortly

CC @ideasman42

Checked on this and here are my findings: - the edges currently marked with `geom_inner` (the "working" ones) are from a special case in `bmo_subdivide_edges_exec` where no `SubDPattern` is available for the `SubDFaceData` - for the remaining cases where the pattern-based edge subdivider creates those "missing" edges edges are not flagged `ELE_INNER` - there are many different patterns, but afaict, the fundamental operation in all of them is `connect_smallest_face`, so easiest solution would be to flag new edges there - (or maybe this needs more flexibility in that one could pass in which flag to use? made optional entirely?) Will post a Diff shortly CC @ideasman42

Philipp Oeser removed their assignment 2022-01-18 21:18:16 +01:00

Philipp Oeser commented

2022-01-18 21:18:16 +01:00

Will have to concentrate on triaging for a while (and step down).

Philipp Oeser removed the

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bmesh.ops.subdivide_edges doesn't report all inner edges in 'geom_inner' #83926