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Problem with bevel modifier
Closed, ResolvedPublic


System Information
win7 64

Blender Version
Broken: 2.78.4 3ceb68c

Short description of error

Clamp Overlap in Bevel Modifier affects all edges instead of only those that are too close



Event Timeline

Can you be more specific and write the steps you are taking?
it's my understanding that clamp works on all edges that are being beveled,
not allowing them to have overlapping collisions, BUT allowing them to be beveled.

Aaron Carlisle (Blendify) triaged this task as Needs Information from User priority.

Please also add a blend-file.

1.Create any mesh
2.Apply bevel modifier with clamp On
3.Move any edge close to another

If I understand wiki correctly, with "clamp overlap" weight of bevel should change only for edges that are close, not for entire mesh.

Aaron Carlisle (Blendify) raised the priority of this task from Needs Information from User to Needs Triage by Developer.Apr 17 2017, 4:50 PM
Sergey Sharybin (sergey) triaged this task as Normal priority.

@Howard Trickey (howardt), afraid another one for you. Will leave it up to you to decide whether those all the same issues or not :)

Sorry, the behavior mentioned here in this bug (T50994) is the intended behavior. The clamp that is calculated is a GLOBAL clamp for the offset amount, calculated as the minimum amount that might cause overlap (approximately -- doing it exactly is hard, and a TODO). The reason for this is so that the bevel looks uniform when done -- that is, the widths all look about the same. In some artistic contexts, it could look strange to have some edges beveled a lot and some edges beveled a little (e.g., you might want all edges of a table beveled approximately the same).

One can (usually) get the effect you want by applying two bevel modifiers with different widths, applying two separate sets of edges.

I can understand that the opposite argument could hold: one could get the effect of uniform edges by simply noting where the clamp starts to take effect and use that as the amount. However this would break backward compatibility. In fact, as a bit of history: there didn't used to be a clamp option for bevel when we first made it work for 2.5, but it turned out there were existing models where the amount had been set very large and the artist relied on clamp to make the result uniform.

Since 2.8 is allowed to break backward compatibility, we could consider changing the behavior to the way you want for 2.8, but I would want to see some consensus from artists that this is desired.

For now I am closing this bug and putting your desire into the general tracking bug for desired bevel improvements, T48583.