bevel modifier behave weird with screwed object #39486

New Issue

Jakub Strykowski · 2014-03-28T14:48:26+01:00

Jakub Strykowski commented

2014-03-28 14:48:26 +01:00

Blender Version
Broken: 2.70 official

**Showed on image, when profile is not rotated bevel looks good, but when rotate by 45' it makes mess

**Blender Version** Broken: 2.70 official **Showed on image, when profile is not rotated bevel looks good, but when rotate by 45' it makes mess {[F83212](https://archive.blender.org/developer/F83212/bevel_bug.jpg)}[bevel_bug.blend](https://archive.blender.org/developer/F83214/bevel_bug.blend)

Jakub Strykowski commented

2014-03-28 14:48:26 +01:00

Changed status to: 'Open'

Jakub Strykowski commented

2014-03-28 14:48:26 +01:00

Added subscriber: @cenobi

blender-admin commented

2014-03-28 14:48:26 +01:00

#40100 was marked as duplicate of this issue

blender-admin commented

2014-03-28 14:48:26 +01:00

#39499 was marked as duplicate of this issue

Bastien Montagne commented

2014-03-28 15:23:08 +01:00

Added subscriber: @mont29

Howard Trickey was assigned by Bastien Montagne

2014-03-28 15:23:25 +01:00

Bastien Montagne commented

2014-03-29 11:43:48 +01:00

Added subscribers: @alihakkidemiral, @gwentiv

Bastien Montagne commented

2014-03-29 11:43:48 +01:00

◀ Merged tasks: #39499.

Howard Trickey commented

2014-03-31 14:54:58 +02:00

I agree that something funny is going on here, and will try to debug it.

Howard Trickey commented

2014-07-21 01:07:41 +02:00

Finally looked at this. Uploaded another .blend that is easier to test with.
screw.blend

The problem is that the twist means that there is no perfect place for the beveled verts to go such that the offset distance from the original edge is the spec, at both ends. So it chooses a compromise place that happens to make the one side about 2% too wide and the other about 2% too narrow. There is an adjustment pass that tries to make both ends of the bevel have the same width. Unfortunately, that pass keeps making one side 2% narrower and the other side 2% wider at each edge. After several hundred edges, one side seems to have almost zero width, and the other side is much bigger than the spec.

I need to either (1) find a smarter algorithm for the width adjustment that doesn't allow this accumulation; or (2) add an option to "not try to adjust widths". The latter would fix this case but it is really annoying to accumulate flags whose only purpose is to work around problems that otherwise occur. So will try for a smarter algorithm first.

Finally looked at this. Uploaded another .blend that is easier to test with. [screw.blend](https://archive.blender.org/developer/F98710/screw.blend) The problem is that the twist means that there is no perfect place for the beveled verts to go such that the offset distance from the original edge is the spec, at both ends. So it chooses a compromise place that happens to make the one side about 2% too wide and the other about 2% too narrow. There is an adjustment pass that tries to make both ends of the bevel have the same width. Unfortunately, that pass keeps making one side 2% narrower and the other side 2% wider at each edge. After several hundred edges, one side seems to have almost zero width, and the other side is much bigger than the spec. I need to either (1) find a smarter algorithm for the width adjustment that doesn't allow this accumulation; or (2) add an option to "not try to adjust widths". The latter would fix this case but it is really annoying to accumulate flags whose only purpose is to work around problems that otherwise occur. So will try for a smarter algorithm first.

Howard Trickey commented

2015-03-20 12:49:47 +01:00

Added subscribers: @00Ghz, @MarcClintDion, @howardt, @JulianEisel

Alexey commented

2015-05-19 21:25:06 +02:00

Added subscriber: @Inwader77

blender-admin commented

2015-08-16 21:15:13 +02:00

This issue was referenced by 0c420a2e49

This issue was referenced by 0c420a2e496963c3f2730333a2c09f788efba39b

Howard Trickey commented

2015-08-16 21:21:08 +02:00

Changed status from 'Open' to: 'Resolved'

Howard Trickey closed this issue

2015-08-16 21:21:08 +02:00

Howard Trickey commented

2015-08-16 21:25:26 +02:00

Note that I gave up trying to make an algorithm that works well in all cases. I could fix the bug in this report by clamping the amount of width adjustment in the global width adjustment path; but that made one of the regression tests look bad.

But I really didn't want to add a flag meaning "do global width adjustment" because I felt it would be hard to explain to users. Luckily, the 'Clamp overlap' flag already has a kind of similar meaning -- "don't let the parameters get so out of control so as to make the result crazy". And also luckily, that flag is on by default in the bevel modifier. So I decided to have the clamping effect happen only when the "Clamp overlap" flag is on, which means that the bevel_bug.blend example in this bug now works fine.

Note that I gave up trying to make an algorithm that works well in all cases. I could fix the bug in this report by clamping the amount of width adjustment in the global width adjustment path; but that made one of the regression tests look bad. But I really didn't want to add a flag meaning "do global width adjustment" because I felt it would be hard to explain to users. Luckily, the 'Clamp overlap' flag already has a kind of similar meaning -- "don't let the parameters get so out of control so as to make the result crazy". And also luckily, that flag is on by default in the bevel modifier. So I decided to have the clamping effect happen only when the "Clamp overlap" flag is on, which means that the bevel_bug.blend example in this bug now works fine.

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bevel modifier behave weird with screwed object #39486