how do you make those 3d-models, especially the more complex structures? .. here’s my reply.

Well, it’s an ambitious task to to it but it isn’t so superhard as it seems. The main difficulty is to get hi-res satellite imagery and some information on building levels and height. Another difficulty comes from the blind modelling approach in JOSM. You can get some help from the Kendzi3d Plugin, but I don’t make use of it. So it’s always a little surprise what the rendering engines does with the uploaded changeset. I’m not a big fan of commercial F4mapDemo with its animated objects. I prefer to see good results on OSMbuildings and OSMgo

I usually start with a floorplan, which could be found on wikipedia or other building related websites. You can resize it to match your favourite scale. When it comes to building parts i make use of the building symmetry. The roof shapes could be estimated from the hi-res satellite imagery. But there’s no height information apart from the shaddow length. So if there’s nothing on wikipedia, emporis, streetview or other, I use some photogrammetry tricks to get the information I need. I often combine some simple structures to achive a higher complexity. But I try to keep it as simple as possible. I also avoid to use multi-polygons, cause their roof will never be rendered the way I want it. Finally i check that all parts won’t overlap with the building outline and put everything in a single building relation. That’s it.