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Bevel tool (and modifier) doesn't work properly
Closed, InvalidPublic

Description

System Information
Operating system: windows 10
Graphics card: gtx 1080

Blender Version

2.80.35

Short description of error

Bevel tool doesn't work as it should in this case - shown in the screenshots. It also concerns 2.79 version

Details

Type
Bug

Event Timeline

Vlad (Vladko) updated the task description. (Show Details)Dec 5 2018, 9:39 PM

Yes, I see the problem. You can work around it by turning off the 'Loop Slide' option.
There's some complicated optimization that goes on to try to even out the loops when loop slide is on, and looks like there might be a bug in that.

OK, I finally found time to look at this. Unfortunately, I am going to close this as "working as intended". The workaround cited above (turn off Loop Slide) should be satisfactory in cases like this.

Some more explanation:
When 'Loop Slide' is on, it sets up a frequently unsolvable set of constraints on what the solution is supposed to do. We want the bevel widths to match their specified widths, but that is impossible if the intersection between two adjacent beveled edges is forced by 'Loop Slide'. So there is an optimization pass which tries to keep the bevel widths as even as possible while matching the specs as closely as possible. In this case, the place where the angled up connecting edge occurs is where the width of the long beveled edge differs from the spec by being smaller (in order to not distort the width too much along the bottom) and that forces an intersection point that is angled up. Other than giving the user more control over what to favor in the optimization step ("even widths" vs "spec width matched"), I don't know how to solve this problem.
I checked and the math for the optimization problem was correct. When I originally got this report, i wondered whether I had made a mistake there, but no I did not.