Bevel modifier: Unnecessary clamping
Open, ConfirmedPublic

Description

System Information
Windows 10 (x64) (version 1703), GTX 750Ti

Blender Version
Broken: 2.78c and latest build blender-2.78.0-git.2836003-windows64

Short description of error
When the bevel modifier's "Clamp overlap" option is active, clamping is applied even though it's not required.

Exact steps for others to reproduce the error

  1. Open the attached file that I reduced to the most simple example
  2. Repeatedly switch the "Clamp overlap" option on and off to see that it affects the mesh.

I expect the option not to affect the mesh because there is no overlapping even if the option is inactive. This case is different to other reported cases as there is only one edge involved.

Please note that, if you move the three top vertices upwards (in Z direction), clamping is not performed anymore. However, this shouldn't make a difference in this case.

Thanks.

Details

Type
Bug

This should probably be merged with T50994 and T50819

Howard Trickey (howardt) raised the priority of this task from Normal to Confirmed.May 29 2017, 9:09 PM

This is different from T50994, as it is only about one edge (as reporter notes). It may overlap with one of the problems reported in T50819, premature clamping. I will look into this one now.

The problem is that the clamping is very naive right now: just clamps to the min of the half-length of all the edges involved in a vertex bevel. In this case, that means it clamps to the half length of the vertical edge, which doesn't even have advancing vertices on it, and it is a lot shorter than the edge that the vertices move along. It is a TODO to do much smarter clamping, but I'll spend some time now to see if cases like this, at least, can be improved.