Converting CRS from EPSG:31256 to EPSG:4978 generates incorrect tiles

[gafert]

When converting a 3D City Database with EPSG:31256 to 3D tiles for cesium with EPSG:497 the postion on the globe is incorrect. Also the normals (not sure about that) and the positions are flipped.

I used the following command:

citygml-tiler -i CityTilerDBConfig.yml --type building --crs_in EPSG:31256 --crs_out EPSG:4978

The data I used is from https://www.wien.gv.at/ma41datenviewer/public/start.aspx called
"Generalisiertes Dachmodell (LOD2.1)" in the EPSG:31256 format, as is the database.

I followed the guide at https://github.com/VCityTeam/py3dtilers/blob/master/docs/Doc/cityGML_to_3DTiles_example.md

Here is an example image rendered in CesiumJS:

Also: I tried another way to change the CRS described at the bottom of this page: https://3dcitydb-docs.readthedocs.io/en/latest/impexp/import.html. Altough the reprojected mesh is a bit buggy its at least at the right postion. I guess there are multiple ways to reproject at this is using a lower resolution algorithm. At least I know the data is correct.

Is there any way to to reproject the cityGML correctly?

[andreiveselov]

Could it be due to the fact that EPSG:31256 is using different axis order, i.e. X and Y axis are swapped.? https://spatialreference.org/ref/epsg/31256/html/
Might need to debug reprojection code if this is the case. I belive, pyproj should be able to handle it.