I am interested in mapping the heights of a building. The elevation of the top of the building is always the same. The bottom of the building rises with the hill.
I have drawn an example shape. (See image: )
The floor labelled ‘0’ in the image is the main entrance, and corresponds to the lowest floor in the building.
My initial idea of using building:min_level=* meant that the building floats above the ground, whereas .
Can’t see a picture but the case is clear, I think. The zero height point can be considered to be the point where the overall building outline meets the lowest ground. Where the ground is higher than this, the building can be expected to be automatically embedded into this higher ground (eg in F4map view with ground contours turned on). So if there are no other steps apart from the base, you could just model the whole area as a single building with the height as the distance of the top above the lowest ground.
If you want to record the absence of the below-ground floors, divide it into building:part areas (covering between them the full plan area of the building), and set the min_level appropriately as 1,2 etc for the number of ‘missing’ floors in each bit.
If this is shown without ground shape available/ turned on (or if the 3d viewer’s ground doesn’t slope like reality - noting that any ground level/shape is not part of OSM itself and isn’t controlled with OSM data) it will be possible to see under parts of the building.
You can (and probably should) set height and min_height as well as building:levels and building:min_level. So an option to consider is to set the building:min_levels to make the numbers of floors right in each building:part area, but set the min_height values less than the typical 3m/level so the building will be less likely to be seen as undercut, by allowing some the ‘foundations’ to be seen if the ground isn’t well drawn.
This bit is probably not a good idea because it will affect at which elevation each level starts, and how high the level itself is – windows will not line up between the building parts and so on.
Apart from that, I agree with the answer. It will only look right for 3D renderers that support terrain elevation, but that’s inevitable with such a building.