Inverted normals when using shell and fillet

[blastrock]

The following code with a negative shell works fine:

test = (
    cq.Workplane("XY")
    .box(10, 10, 10)
    .faces(">Z")
    .shell(-1, "intersection")
    .edges("|Z")
    .fillet(1)
)
show_object(test)

However, if we make the shell positive, the normals get inverted and we get "holes" in the shape

test = (
    cq.Workplane("XY")
    .box(10, 10, 10)
    .faces(">Z")
    .shell(1, "intersection") # <----- positive shell
    .edges("|Z")
    .fillet(1)
)
show_object(test)

It works fine without the fillet.

Version: 2.3.1_43_gad46448

[jmwright]

I am unable to reproduce the visual error with the VTK-based show feature, but I can with CQ-editor (latest master). Also, when I export to STL with negative shell there are no mesh errors, but when I export to STL with positive shell, there are over 1500 errors that are auto-repaired.

VTK-based show:

CQ-editor:

STL Errors:

[adam-urbanczyk]

test.val().isValid() returns False. In general the shell function is not always reliable. You can using test.val().fix()