Publishing Civil3D files

Preparing DWG files for successful publishing into iModel

• Set correct units in DWG files
  • DWG is a unitless file format.  However, it has a system variable called LUNITS, aka Design Center Units.  When LUNITS is set to real-world units, the units will be used for iTwin.
  • When LUNITS is set to Unitless, a DWG connector will make the best effort to infer possible units used in a DWG file, but it is not reliable. 
  • You should always try setting the correct units using LUNITS.  Setting correct units in a source DWG file will ensure you get the correct units in iTwin.
• Create Global Coordinate System (GCS) using MAPCSASSIGN in AutoCAD Map or Civil3d, but not in AutoCAD
  • A MAP based product creates GCS’s of grid coordinate system, which is supported by DWG connectors

AutoCAD creates GCS’s of the local coordinate system, which is not supported by DWG connectors.

• If a DGN file is mapped as a root spatial model in the iModel, its GCS may or may not be right for DWG file.
  •  DWG files that have been attached as reference files in the root DGN file will be connected by DGN based connectors, therefore these models will be correct in the iTwin.
  • DWG files that are mapped separately as master files, alongside the DGN root spatial model, must have model coordinates aligned with the GCS from the DGN file.  Otherwise, DWG models may not be located correctly in iTwin.  A quick way to check if a DWG model can align with the DGN spatial root model is to try referencing the DWG file in the root DGN file using MicroStation.  Make sure you use the default attachment method, Align With the Master File (aka as Coincident attaching).  If the DWG model looks correct in MicroStation, it will be located correctly in iTwin.  If it looks wrong in MicroStation, it will be incorrect in iTwin.

• Similarly to a DGN root model, if a separate/different DWG file is mapped as a spatial root model in the iModel, its GCS may or may not be right for other DWG files.

  • The root DWG file should have a GCS assigned using the aforementioned tool MAPCSASSIGN
  • All other files intended to be mapped into iTwin should have coordinates matching the GCS in the root file
  • You can test that simply by attaching other DWG files to the root DWG file at the world origin 0,0,0.  You can do this in either MAP or Civil3d.
  • If an xReference file is not aligned correctly in MAP or Civil3d, move model space entities in the xReference file (as opposed to moving xReference attachment in the root file), or use a correct GCS in the root file with MAPCSASSIGN.