Freestyle rendering artifacts with subdivision modifier, bug or intended?

Hey all!
Hopefully I’ve posted this in the right section, if not I humbly apologize!

I’m currently assisting two manga artists in Japan with technical and environment renders, and I’ve stumbled upon an annoying, though not showstopping behavior of the renderer. I’m still new to the Freestyle workflow, thus this might be my own fault for not knowing.

That said, here’s an example:

The mesh to the right has a mirror and subdivision modifier.
The middle has the mirror applied, but still has a subdivision modifier.
The left has the mirror modifier, but the subdivision modifier has been applied.

This only seem to happen so long the subdivision modifier is present, once applied everything renders as intended. Thus I’m wondering, is this intended behavior or is it a bug?


It may be intended behavior.
When, subdivision modifier is applied, geometry shape is smoothed. Maybe vertices that are supposed to be at center of mesh are a little bit shifted.
So, maybe, Freestyle is interpreting that object as 2 parts, creating those artefacts.
Maybe, if you increase merge limit of mirror modifier, fusion of doubled vertices at middle of mesh will be more solid. Maybe it could be sufficient to fix the problem.

Cheers for your suggestion!

Sadly though, the mirror modifier has no effect on this.

The artifacts seem to be edges that aren’t visible, yet are rendered for some reason. This only happens if the subdivision modifier isn’t applied and on the stack, once applied and removed from the stack, it renders correctly. Which leads me to believe something isn’t working as intended between the Freestyle renderer and the subdivision modifier, though I might be mistaken.

Left: Subdivision modifier on the stack.
Right: Subdivision modifier applied and removed from the stack.

Would be nice to be able to keep the subdivision modifier, as making changes later to the mesh would become rather cumbersome.

Scene file below, if anyone has the time to check.