Snow not on all top parts of custom buildings (engine bug?)

Hi there,

I have a weird problem regarding snow coverage of buildings. Here is what I did:

  1. I built several buildings for a custom airport scenery in Blender.
  2. I use the same material, using one texture. After modelling and texturing, I join the geometry to make it one object, center it at origin of the world and export it to MSFS.
  3. After building the package, the object shows as intended in the SDK scenery editor.

4. When I set the weather to snow, only parts of the (sloped) roofs have snow on top of it, depending on the angle it seems.
5. When I rotate the building(s), I can get them to angles where the roof is fully covered in snow.

6. That the SDK is internally “confused” how the building is actually oriented, meaning where is top, where is bottom.

However, since I build it in a very straightforward way within Blender and center everything before exporting, that does not make sense to me. With some buildings some side of the roof is covered, with others the whole thing (weirdly the most complex one, a hangar with softly sloped roofs), with others none.

I am lost, as I cannot foresee when it will work and when not.

Any ideas? Thank you!