Line art modifier affects random objects

Question

[EDIT] Someone told me a fix using masks and collection mask. I'll answer with the fix asap

I have a grease pencil object with a line art modifier that modifies a collection called "40":

The problem is that the modifier affects some objects placed OUTSIDE the "40" collection. In this screen capture I marked the black lines that should not appear:

Here it is the file for review

Is this a bug or something I'm doing wrong? Thank you.

Answer 1

As I told you in the comment, You can uncheck Intersection but you will loose the intersections from the selected collection too (you can try it to see what I am talking about) so it may not be an option.

While playing around with your file tho, I managed to find a somewhat decent result :

As you can see the unwanted lines are gone and you still have the intersections in your collection.

You need to leave Intersection checkbox checked for the following to work.

In the modifier, you have a section called Intersection :

The little box that you see there allows you to mask the collections from the modifier. I don't really know how those work but if you tick the first box (or any of the others), the unwanted lines disappear :

But you'll also loose the intersections that you want to appear.

To bring them back, there is a section called Chaining :

If you tick the first checkbox : , you'll bring back the intersections while keeping the unwanted ones away :

As a disclaimer, I have to admit you that, I don't completely understand how/why it works, I just played around with the settings and kind of stumbled on this by accident so this may not work with other scenes but it seems to work well with this one.

I am not sure, either, if this behavior is a bug or if it is really what is expected to be like. Anyway I hope I helped you.