Operating system: Windows 10 Home
Graphics card: GTX 1060
Boolean Union is treated as Difference and vice versa when a mesh is generated with mirror modifier.
Steps to reproduce:
- Get any mesh, use a cube to carve a piece of geometry out using Boolean modifer set to 'Operation' to Difference.
- 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.
- Apply mirror modifier, separate the meshes.
- 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.