Hi, false1. In object mode, under the tools tab, those settings for smooth shading or flat shading do not change the mesh topology. They are simply a display shading algorithm which "fakes" the appearance of a smooth surface using some lighting and normals tricks. This information does not really do anything to the geometry, although the information can be passed through some export file formats like OBJ as well. Subdivision smoothing or relaxing the mesh, on the other hand, does affect the topology itself, and what you see is actually what you get in those cases.

Using Relative paths to external files is typically a good idea if you are going to share scenes or redistribute your content for others to use. The error may be related to this if the addon is relying on absolute paths internally, but I'd be surprised to know this is the case. It may ver well be however. Do you have any documentation over at SceneCity? Here's some more detailed info regarding relative paths from the Blender documentation itself:

https://www.blender.org/manual/data_system/files/relative_paths.html

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