Manual: Subdivide fails to subdivide N-Gon faces isn't clearly documented #73667
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Reference: blender/blender-manual#73667
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Blender Version
Broken: version: 2.82 (sub 6), branch: master, commit date: 2020-02-06 20:44, hash:
blender/blender@763f117c48
Short description of error
The manual doesn't mention that Subdivide may fail to execute on all selected faces.
Exact steps for others to reproduce the error
SubdivisionMayIgnoreSelection 2020-02-07.mp4
https://docs.blender.org/manual/en/dev/modeling/meshes/editing/subdividing/subdivide.html#bpy-ops-mesh-subdivide
Added subscriber: @EVH1
Added subscriber: @EAW
Changed status from 'Needs Triage' to: 'Confirmed'
This I cannot reproduce. In your video, we cannot tell if the edges are subdivided because you are in face select mode. When I tried using today's daily build, the edges are clearly subdivided once I switch to vertex select.
Edges not subdividing and faces not subdividing are two separate things. The 4 faces you are expecting to be subdivided all have 5 vertices and 5 edges at the beginning of your video.
Looking at the manual, it seems that subdivision will only subdivide the face of a quad or a triangle, but not N-GONs.
You have to really read between the lines to get that, so I would consider this a case of unclear documentation since it isn't directly mentioned on the manual's subdivision page.
Subdivide fails to subdivide all selected facesto Manual: Subdivide fails to subdivide N-Gon faces isn't clearly documentedI'm not sure where I mentioned edges were not subdividing? Those did subdivide.
In the video, Blender was displaying a point at the center of each face, but those points were not connected (nor editable) as you can see from a lack of edges to the center points. The steps listed began with a cube which was all quads unless a cube is actually two quads and a strip of quads internally. What's interesting is that the edges of all selected faces were subdivided and the faces were recreated to incorporate the new vertices thereby becoming n-gons for those faces that failed to subdivide. That's where the problem lies.
I hope you'll reconsider looking into this further.
On the topic this ticket transitioned into:
Subdividing triangles and n-gons can make for strange lighting/texturing results in certain scenarios, but it should be something the subdivision routine handles without geomtery deformation when smoothing is off. This can be done as follows:
When smoothing is enabled, it's possible that curved geometry may start to look more faceted visually, but that should always be something that is left for the user to decide. Subdivided geometry with smoothing disabled should look the same even if an n-gon is allowed to have holes, assuming the cutouts were calculated correctly. Blender aside, subdividing is not impossible for n-gons, so I'm hoping that doesn't get blocked -- at least not permanently.
Thanks
This issue was referenced by 6206
Changed status from 'Confirmed' to: 'Resolved'