I've been looking to get into this as a means of creating/updating the NYC massing my office uses, especially since nyc.gov has GIS, etc., info available publicly and has its own model for download (dgn/esri/gml formats). There is also the TUM study available (which is huge in size).
The issue is I have little understanding of how to properly use these files. I have managed to open some of the gml files in FZK Viewer, in which I can export them to stl and open in MAX. I was wondering if there is a better solution, such as using FME, 3D City DB or something else. Basically looking to, in the simplest means, convert the dgn/gml files to obj/fbx. I've tried the dgn format from nyc.gov in CAD, however it imports as polylines and not surfaces/3d solids.
Also if anyone knows how to just use OSM data and where to import it to as to convert it to 3D (utilizing JOSM/OSM2 World, etc).
Any insight/advice would be helpful and much appreciated.