[bmesh]calc_vert_angle does not return the correct value. #43904

New Issue

perfection cat · 2015-03-06T02:29:15+01:00

perfection cat commented

2015-03-06 02:29:15 +01:00

System Information
Windows XP/SP3 32bits

Blender Version
Broken: version 2.73 (sub 9), version 2.73 (sub 0), 2.71
Worked: unknown

Short description of error
[bmesh]calc_vert_angle does not return the correct value.

Exact steps for others to reproduce the error
[bmesh]calc_vert_angle does not return the correct value.

This returns the correct value.

**System Information** Windows XP/SP3 32bits **Blender Version** Broken: version 2.73 (sub 9), version 2.73 (sub 0), 2.71 Worked: unknown **Short description of error** [bmesh]calc_vert_angle does not return the correct value. **Exact steps for others to reproduce the error** [bmesh]calc_vert_angle does not return the correct value. ![wrongbmeshangle.png](https://archive.blender.org/developer/F147485/wrongbmeshangle.png) ![wrongbmeshangle2.png](https://archive.blender.org/developer/F147487/wrongbmeshangle2.png) This returns the correct value. ![wrongbmeshangle3.png](https://archive.blender.org/developer/F147489/wrongbmeshangle3.png)

perfection cat commented

2015-03-06 02:29:15 +01:00

Changed status to: 'Open'

perfection cat commented

2015-03-06 02:29:15 +01:00

Added subscriber: @sindra1961

perfection cat commented

2015-03-06 02:34:14 +01:00

When edge sharing vertex is not only two, which edge is chosen?
In that case, can it appoint edge?
wrongbmeshangle.blend

When edge sharing vertex is not only two, which edge is chosen? In that case, can it appoint edge? [wrongbmeshangle.blend](https://archive.blender.org/developer/F147493/wrongbmeshangle.blend)

blender-admin commented

2015-03-06 08:55:36 +01:00

This issue was referenced by 8638142c3b

This issue was referenced by 8638142c3bf1d0701a08d3222366fcd92d3e7772

Campbell Barton commented

2015-03-06 09:04:01 +01:00

Changed status from 'Open' to: 'Resolved'

Campbell Barton closed this issue

2015-03-06 09:04:01 +01:00

Campbell Barton commented

2015-03-06 09:04:01 +01:00

Closed by commit 8638142c3b.

Closed by commit 8638142c3b.

Campbell Barton commented

2015-03-06 09:05:12 +01:00

Added subscriber: @ideasman42

Campbell Barton commented

2015-03-06 09:05:12 +01:00

This wasn't working usefully.

Renamed to calc_edge_angle, now it takes an optional fallback value when the vertex doesn't have 2 edges connected. If no fallback is given it raises an exception.

This wasn't working usefully. Renamed to `calc_edge_angle`, now it takes an optional fallback value when the vertex doesn't have 2 edges connected. If no fallback is given it raises an exception.

blender-admin commented

2015-03-06 17:24:10 +01:00

This issue was referenced by 720599e7a8994e73b47fba76cabe946ab241e1be

perfection cat commented

2015-03-07 04:07:24 +01:00

I thank for what you revised, but do not think that the correction has a meaning.
How long will vertex shared only to two sides exist?
There are four in Plane.
There is nothing in Cube.
I want you to think about how many such vertex there are in a primitive object.
The grand total of the angle between all edge sharing vertex.
Or an angle between edge chosen from edge which shared vertex.
I think that it can include a useful function.
I think that it is easy to use a latter function personally.

I thank for what you revised, but do not think that the correction has a meaning. How long will vertex shared only to two sides exist? There are four in Plane. There is nothing in Cube. I want you to think about how many such vertex there are in a primitive object. The grand total of the angle between all edge sharing vertex. Or an angle between edge chosen from edge which shared vertex. I think that it can include a useful function. I think that it is easy to use a latter function personally.

Campbell Barton commented

2015-03-07 05:27:33 +01:00

This value doesn't have a single/correct answer, since many disconnected faces can use a vertex.

You can for example - take the angle between the vertex normal, and one of the faces that use it. or all of them. then accumulate the difference (weighted by the face-angle).

Blender has a function called BMVert.calc_shell_factor() that does this, but it is just an approximation.

You could do:

  f = v.calc_shell_factor()
  angle = math.acos(1.0 / f)

This value doesn't have a single/correct answer, since many disconnected faces can use a vertex. You can for example - take the angle between the vertex normal, and one of the faces that use it. or all of them. then accumulate the difference (weighted by the face-angle). Blender has a function called `BMVert.calc_shell_factor()` that does this, but it is just an approximation. You could do: ``` f = v.calc_shell_factor() angle = math.acos(1.0 / f) ```

perfection cat commented

2015-03-07 05:54:43 +01:00

This comment was removed by @sindra1961

*This comment was removed by @sindra1961*

perfection cat commented

2015-03-07 06:36:35 +01:00

@Campbell: This is correct?

shellfactor.blend

@Campbell: This is correct? ![screen.png](https://archive.blender.org/developer/F147866/screen.png) [shellfactor.blend](https://archive.blender.org/developer/F147864/shellfactor.blend) ![screen.png](https://archive.blender.org/developer/F147868/screen.png)

perfection cat commented

2015-03-07 08:23:11 +01:00

@Campbell: Your correction seems to be wrong.

imcomplete.blend

The version that I confirmed
version 2.73 (sub 9), branch b'master', commit date b'2015-03-06' b'16:53', hash b'cf1227d', b'Release'

@Campbell: Your correction seems to be wrong. ![screen.png](https://archive.blender.org/developer/F147874/screen.png) [imcomplete.blend](https://archive.blender.org/developer/F147876/imcomplete.blend) The version that I confirmed version 2.73 (sub 9), branch b'master', commit date b'2015-03-06' b'16:53', hash b'cf1227d', b'Release' ![screen.png](https://archive.blender.org/developer/F147878/screen.png)

perfection cat commented

2015-03-09 02:10:48 +01:00

Added subscriber: @JulianEisel

perfection cat commented

2015-03-09 02:10:48 +01:00

@JulianEisel (Julian Eisel):
I want you to open once again because a correction is not right.

@JulianEisel (Julian Eisel): I want you to open once again because a correction is not right.

Julian Eisel commented

2015-03-09 02:30:54 +01:00

I'd prefer to let Campbell decide that. We usually double check before reopening reports and he is the better man for that ;)

perfection cat commented

2015-03-09 02:35:38 +01:00

@JulianEisel (Julian Eisel):
I understood it. I obey your decision.

@JulianEisel (Julian Eisel): I understood it. I obey your decision.

Campbell Barton commented

2015-03-09 11:39:03 +01:00

re: comment @Sat, Mar 7, 6:23 PM

This is working as expected. A vertex exactly in the middle of 2 edges has 0deg angle. But when on the side of the face, that face-corner is 180deg.

Its just different way of interpreting the value.

re: comment @Sat, Mar 7, 6:23 PM This is working as expected. A vertex exactly in the middle of 2 edges has 0deg angle. But when on the side of the face, that face-corner is 180deg. Its just different way of interpreting the value.

perfection cat commented

2015-03-10 03:49:23 +01:00

@Campbell: I thank for your help.

This function was not the thing which I expected.

@Campbell: I thank for your help. This function was not the thing which I expected.

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[bmesh]calc_vert_angle does not return the correct value. #43904