City (DWG) Import best workflow for 3D printing

Rhino
1

Problem: CityGML → DWG → Rhino → Non-printable geometry

I am working with a city model exported from CityGML (exported as .dwg).
When I import it into Rhinoceros 3D, the buildings are organized into multiple layers (e.g. Building, RoofSurface, WallSurface, GroundSurface, etc.).

Goal

I want to create a clean, closed solid in order to extract a 200 × 200 mm section and prepare it for SLA 3D printing.

Problem

The buildings are not clean, closed polysurfaces, but instead consist of many separate surfaces.
There are numerous naked edges and small geometric inconsistencies.

As a result, the following does not work reliably:

  • Boolean operations

  • Cutting out a solid volume (e.g. a cube)

  • Preparing the model for 3D printing

What I have tried so far

I have already attempted the following steps:

  1. MergeAllCoplanarFaces
    → to simplify adjacent planar surfaces

  2. Join / general repair attempts
    → to create closed polysurfaces

  3. Repair Mesh
    → to fix geometry issues

  4. ShrinkWrap (at the end)
    → to generate a closed volume

Result

  • The model remains messy and fragmented

  • Many naked edges persist

  • Boolean operations are unreliable or fail

  • The model is not suitable for SLA printing

Question

  • Is there a better workflow for CityGML → Rhino?

  • Should I convert to mesh earlier in the process?

  • Is there a robust way to unify/clean this type of geometry?

    Muensterhuegel_ohne_Dachueberstaende.dwg (3.8 MB)