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Boolean modifier union/difference are inverted based on cutout mesh generation method
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Description

Operating system: Windows 10 Home
Graphics card: GTX 1060

Broken: 2.82

Boolean Union is treated as Difference and vice versa when a mesh is generated with mirror modifier.

Steps to reproduce:

  1. Get any mesh, use a cube to carve a piece of geometry out using Boolean modifer set to 'Operation' to Difference.
  2. Add a mirror modifier to the cube and mirror it over X axis. (handedness change?)

Result: You will see that the mirrored portion of the mesh does not boolean properly.

More Evidence:

  1. Apply mirror modifier, separate the meshes.
  2. Try to boolean the new cube into your mesh. You will see that you cannot use Difference as a cutout now, you have to use Union.


Event Timeline

I don't understand the bug.
The attached file doesn't even have the mirror modifier.

It would be nice if you could simplify the file or be more specific about what the bug is.

Thanks for feedback, edited description to read more easily, updated image and .blend in the same way.

The report seems correct. But don't know if it is a bug or a limitation (& thus feature request )

Hans Goudey (HooglyBoogly) changed the task status from Needs Triage to Needs Information from User.Apr 24 2020, 11:18 PM

Thanks for the report, I can't reproduce this though. Could you specify a version where this worked in your case?

Either way, we'd have to see if you could still reproduce the problem in 2.82. And we'd have to find that it's not a problem with Boolean, which is being rewritten from scratch.

I can't reproduce this though.

In the file, there needs to be another cutout, as per OP, mirror opposite to the original cubes, which is not there.

More than a week without reply or activity.
Due to the policy of the tracker closing for until required info/data are provided.

If the problem persists please open a new report with the required information.