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"Set normal from faces" operator does not work in a sensible way, needs decision on what is expected behavior here.
Open, Confirmed, LowPublic

Description

Reading current code of that operator, it's not making much sense…

  1. It computes some averaged vertex normals out of select faces' normals only (without even complying to our generic, weighted computation for that).
  2. It then does two different loops (over selected verts of edges of faces first, then over loops of verts), to set some custom normals to those weirdly averaged vertex normals computed at step 1.

I think what it is supposed to/trying to do here is actually the following:

  1. For each clnor fan (i.e. set of contiguous faces around a given vertex, delimited by sharp edges, that share the same custom normal), properly compute the averaged normal from selected faces, and set it.

This will give predictable results, when a single face is selected for each custom normal it will just set to that face's normal, same in case all edges are sharp… And the 'keep sharp edges' option is not needed anymore, I do not see the reason for that one anyway, if you do not want a sharp edge, just do not tag it as such. ;)


Original Report

System Information
Operating system: Windows-10-10.0.17134 64 Bits
Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 417.35

Blender Version
Broken: version: 2.80 (sub 60), branch: master, commit date: 2019-05-09 17:55, hash: rB427c75e4c20b
Worked: (optional)

Short description of error
[I can not use set normals from faces when selecting a specific face. When I split normals/make em sharp I expect that I can control specific face normal without it interfering with the other normals, this is at least how you do it in all other 3d packages]

Exact steps for others to reproduce the error
[Split/ make all edges sharp, select all vertexes, go to mesh/normal/rotate to make all normals crazy. Now try to set the normals from one of the faces.

]
[Based on the default startup or an attached .blend file (as simple as possible)]

Details

Type
Design

Event Timeline

By quick glance this will work on all associated loops of the corresponding vert.
(I see the point where this is not desirable)

I think this could be changed to only alter loops of selected faces [at least if Keep sharp Edges is ON]

@Bastien Montagne (mont29): not sure this is considered a bug? Should we put this on TODO [could try my luck on this if desired...]?

Thank you for looking into this! It is crucial for game dev to be able to have full control of the normals.

The thing is that this used to be a "bug" and it got fixed a couple a months ago, but now it is back again.

Sebastian Parborg (zeddb) triaged this task as Confirmed, Medium priority.
Bastien Montagne (mont29) lowered the priority of this task from Confirmed, Medium to Needs Information from User.Jun 11 2019, 5:41 PM

Hmmmpf… reading code of that operator, it's not making much sense…

  1. It computes some averaged vertex normals out of select faces' normals only (without even complying to our generic, weighted computation for that).
  2. It then does two different loops (over selected verts of edges of faces first, then over loops of verts), to set some custom normals to those weirdly averaged vertex normals computed at step 1.

I think what it is supposed to/trying to do here is actually the following:

  1. For each clnor fan (i.e. set of contiguous faces around a given vertex, delimited by sharp edges, that share the same custom normal), properly compute the averaged normal from selected faces, and set it.

This will give predictable results, when a single face is selected for each custom normal it will just set to that face's normal, same in case all edges are sharp… And the 'keep sharp edges' option is not needed anymore, I do not see the reason for that one anyway, if you do not want a sharp edge, just do not tag it as such. ;)

@Johan Ernstsson (Ernstsson) you claim that that was already reported and fixed, would be interested to see that previous report, might shed some light on that topic.

PS: I would not rush a fix here for 2.80 anyway, that code has been working that way since the beginning afaict, so this is more a TODO than a bug really.

Bastien Montagne (mont29) changed Type from Bug to Design.
Bastien Montagne (mont29) renamed this task from Set normal from faces do not respect sharp or splited normals. to "Set normal from faces" operator does not work in a sensible way, needs decision on what is expected behavior here..
Bastien Montagne (mont29) lowered the priority of this task from Needs Information from User to Confirmed, Low.