Hi Michael,

Ah ok, face normals, sorry i am not very aware of the proper vocabulary (when i worked with real clay, vertices and face normals were always just right, haha).

Yes, double sided material solves the problem, exept that the polys remain impossible to select, making material assignment quite painful in modo... (ok you can do it in MoI, but you still need selection in modo for size or position adjustment, etc...)

Fliping in MoI would be great as far as you know which part to flip, but as you can see in the previous image, it would be a tedious work to do here, except if it does a kind of "align" like in modo, that is turning all normals in the same way for a given surface. And here i wonder why this function has no effect in modo, it works just fine usually.

So you're right, the best way is to have a solid.

As for the creases on n-gons, here is a picture (i turned on reflexion mode in viewport for better visualisation, these creases do show in render) :



As you can see, my fillet definition is quite low, this does not happen when i export with more subdivisions. But i have to do an entire town and need to keep the poly count to the minimum. Of course, this does not happen if i export with separate surfaces. Keeping or deleting the vertex normals does not change anything in this case. (note : i redid the export for example and divided plan surfaces here, but the issue is the same with default value for this setting)

Thanks again for your kind help. (and forgive my english, please)

Ambimind, yes you're right, sanity is the hardest thing to keep in this job, haha...