The Top Layer does have two perimeters (most likely due to ensure vertical thickeness) despite single top perimeter option enabled and minimum shell thickness set to 0.
Can be prevented by disabling "ensure vertical shell thickness" but at a value of 0, for shell thickness this very much seems like buggy behavior. Not completely new as it can be reproduced with Version 2.8.1+win64.
slicer_top_bug.zip
Project file & How to reproduce
Slice project file and look at the two perimeters in the top layer (should be a single one).
Delete the modifier to look at the desired result.
PS: This example is useless, but the problem does surface in a vastly more complex part, which I am not able to share due to policy. We tried to provide a minimal example. If needed we can provide a more representative example.
Description of the bug
The Top Layer does have two perimeters (most likely due to ensure vertical thickeness) despite single top perimeter option enabled and minimum shell thickness set to 0.
Can be prevented by disabling "ensure vertical shell thickness" but at a value of 0, for shell thickness this very much seems like buggy behavior. Not completely new as it can be reproduced with Version 2.8.1+win64. slicer_top_bug.zip
Project file & How to reproduce
Slice project file and look at the two perimeters in the top layer (should be a single one). Delete the modifier to look at the desired result.
PS: This example is useless, but the problem does surface in a vastly more complex part, which I am not able to share due to policy. We tried to provide a minimal example. If needed we can provide a more representative example.
Checklist of files included above
Version of PrusaSlicer
Version 2.9.0-alpha1
Operating system
Windows 11
Printer model
Prusa XL 2T