Emmanuel,
I fully understand that it's not simple to find a "one size fits all" solution to compute roofs and ceilings. So maybe a two-pronged strategy, which distinguishes between roofs and ceilings, would work better?
- Ceilings generally are flat.
- Roofs are in a majority of cases non-flat, and/or extend beyond the walls of the building.
I have used other 3D programs, and in general they also make this distinction. Even for non-technical users, it wouldn't be too complicated to understand there is a difference between those two parts of a building.
Hans
PS : When using b19, I draw a rectangular room with a partially sloping ceiling (what you call
sloping 6 points) it generates one sloping roof, without the bend in it. Is it Ubuntu, or did I forget the magic spell?
http://www.mediafire.com/file/wa62c9n9yt5l8py/SlopingCeilingTest#2.sh3d
