Why extrude, lathe, lattice modifiers often screw up normals? is there a way to fix this?

[alexJ682T]

Hello.

My first experience with 3DS MAX was back in 1998, when there was MAX2 version available. These modifiers had mentioned issues quite often. My initial thoughts were "Oh ok, technology is not mature yet, they will fix it some day". Today, after 24 years, these issues are still there?

Simple extrude operation, but it flipped some normals, and there is no easy way to fix it! Have to convert it to editable mesh, enable xview, and manually select and correct all faces. Why?

I'm attaching both screenshot and sample .max file, to showcase the issue. This is a simple stack of circles on a plane, which I want to extrude, but as you can see, extrude decided that some of faces should be reversed 😞 

[BenBisares]

Took a look at your scene and the reason you get some of those "uncapped" extrusions is because the shapes are not closed. If you look at the screenshot below, every circle is open. There are two overlapping vertices that should be just one.
If I weld all of the overlapping vertices then the extrusion appears as expected. Now why did most of them not appear hollow before the weld? Would need to look further into that, but in the end they should be closed as the expectation is hollow extrusions for open shapes.

[alexJ682T]

Yes but problem is, that original vector has everything "closed" and there are no overlapping nodes or whatsoever. Checked the file in both Corel Draw and Artcam (Vector Doctor) - no issues found. So this is 3DS Max, who improperly handles the imported vectors. Below is a screenshot from CorelDraw - showing all vectors are closed and there's nothing overlapping. Thought that there is Adobe Illustrator format import issue within 3DS MAX, so tried to import via DXF - things got even worse - some circles are missing completely! So problem is in 3DS MAX itself. 

Quite curious, why there is no support for .SVG .EMF .WMF .EPS and other, common vector formats?

And for other operators, I'm attaching another .MAX file (This is M2.NVME<>USB Adapter enclosure I've designed for 3D printing, already tested and verified, anyone can use it). Here we have the "case" and the "holes" in it. As I try to "cut" out these holes using Boolean or ProBoolean operators, main surface again gets normals inverted randomly.