Support for curved solids in 3D City Database (e.g., buildings with curved walls)

[Mganjirad]

Hello,

I have a question regarding the geometry support in 3DCityDB.

As I understand, 3DCityDB stores 3D city models (CityGML 3.0) in Oracle or PostgreSQL/PostGIS. My question is:

Does 3DCityDB support solid geometries with curved surfaces (for example, a tower with a curved wall, or a pavilion with curved façades)?

If such curved solids are imported (from CityGML or other 3D formats), are they stored as true curved geometries, or are they automatically approximated/densified into planar polygonal surfaces?

This point is important for us because we need to know whether curved architectural elements can be represented natively in the database, or whether they must always be simplified before storage.

Thanks a lot for your clarification

[thomashkolbe]

Hello Mohammad Ganjirad,
while in principle ISO19107 and the CityGML data model (and the GML encoding) would allow to use curved surfaces as boundaries, 3DCityDB does not support curved geometries, because most established spatial database management systems (like PostGIS and Oracle Spatial) and GIS like ArcGIS or QGIS do not have built-in support for curved surfaces. Hence, you will need to approximate the curved surface, for example, by some triangulated surface before uploading it into the 3DCityDB.
Best regards, Thomas Kolbe

[Mganjirad]

Hello Thomas,

Thank you very much for your clear and detailed explanation. That perfectly clarifies the situation for us. It is very helpful to understand that the limitation is not on the CityGML side, but rather due to the lack of curved geometry support in current spatial database systems and GIS software.

We will therefore prepare our curved models by triangulating or approximating them into planar surfaces before importing into 3DCityDB.

Thanks again for taking the time to explain this so well.

Best regards,
Mohammad Ganjirad