Hi Pilou,

Thank you for trying out some creative ways to attack the problem of getting closed paths!

Re:
> Better if the original objects are Boolean Union and generator vertical
> line of Cylinder hidden

I just tried this on a perspective projection of a more complex object, but the result of boolean union is that most lines get deleted, so maybe union only works for simple cases.

Re:
> Intersection with a plane of the Imported PDF

With more complicated line art this doesn't work for me. I get like 150 planar surfaces with triangular cutouts even though the line art doesn't have any triangles.

Re: Affinity Designer

I've already tried Affinity v2, but it's not good for me. I need a vector eraser, line width tool, and curve offsetting so that when there's a big area I can put hatching as a thin edging around the outside rather than having a large area of stripes that draws too much attention.

Illustrator has a well-known bug in its vector eraser and has a difficult to use width tool, which is why I don't use it for very much. But Affinity completely lacks a vector eraser and width tool, and has unreliable curve offsetting, so for my case it's not as good of a choice as Illustrator. In other words, neither Affinity nor Illustrator are very good for most of what I do, but for the part where I make closed shapes, Illustrator is better than Affinity because it can offset those shapes to make an edging / outline / annular shape around the perimeter.