Top shell generation ignores layer count/thickness requirements

[k1-801]

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Description of the bug

In some cases, the top shell gets only one layer of solid infill on the top, despite having a setting of minimum of more than 1 layers of solid infill there. It only affects the small areas with hollowing infill below them, the rest of this piece gets generated solid as expected.

Project file & How to reproduce

On this screenshot, you can notice the area that generates a non-solid (hollowing) infill (in red) on the very right and very left. On the layer selector on the right you can see that only 2 layers from the top are hidden, so there's only one layer of solid infill (one more layer only contains writings), however, the setting of minimal layer count on top shell is set to 3, and minimal thickness is set to 1mm, which with layers of 0.2mm corresponds to at least 5 expected layers of solid infill.

As you can see, there is one layer of sloid infill below this problematic area, this screenshot shows the sructure below it:

However, if there is no other block with hollowed infill below this place, this also doesn't happen (see a model below for comparison - it has no solid block below the problematic area that gets a hollowing infill): I did not research on how this shape in particular affects the actual generation of the top shell, however, it is probably related to the large bridge area below the part that got solid infill on the screenshot. I loaded the model and set the minimal layer count to 3 and minimal thickness of top and bottom shells to 1mm. I believe this area to be considered a bottom shell by the slicer, since it covers a bridge, and for some reason it affects the outer parts to the sides of the bridge, causing them to also not be considered part of the top shell. The reason for me to believe that is an experiment where I set the minimal thickness to 0, leaving the minimal layer count at 3, which effectively made 2 layers of hollowing infill over the entire part, covered by only 1 layer of solid infill on top. The top layer of hollow infill also had additional solid patches below the embossed writings. Below this hollow structure was 3 layers of solid infill with the same pockets of hollowing infill on the sides:

Project file (only contains the problematic model): Вытяжка.zip

Checklist of files included above

• [X] Project file
• [X] Screenshot

Version of PrusaSlicer

2.5.0+win64

Operating system

Windows

Printer model

Flying Bear Ghost 5

[kubispe1]

I'm trying to investigate it. Modifier brings this problem it seems to me. A cheat to get around this problem is to turn on the provision of vertical wall thickness.

[Jan-Soustruznik]

Hello, @k1-801 ,

I think that the problem is now solved, could you check with latest released version of PrusaSlicer 2.6.0, please?

thank you, have a nice day