Bringing site terrain into Revit and ArchiCAD with IFC and DXF

BIM projects need the ground they stand on. There are two practical routes from open terrain data to a BIM model, and they suit different stages of a project.

Two routes

• IFC: the terrain arrives as a mesh and the surrounding buildings as simple masses, already placed. Best for context, massing studies and views.
• DXF contours: you build the terrain with the software's own tools (a Revit toposolid, an ArchiCAD mesh), so you can edit it, cut it and grade it. Best when the terrain becomes part of the design.

Exporting from TOPOLUMA

1. Set the area and generate the preview in the studio. Keep Terrain and Buildings on in Layers: the 3D formats need at least one of them.
2. In Layers → 3D terrain surface, choose the mesh resolution and, if the site is flat, a vertical exaggeration for presentation (leave it at 1× for BIM).
3. In Export, tick IFC 4 and DXF 2D and download both.

The IFC file is IFC 4 with a map conversion to the site's UTM zone, so it states where it sits on the globe. The DXF is in metres, with contours at their elevation on CONTOUR_MINOR and CONTOUR_INDEX.

Revit

• IFC: use Insert → Link IFC. Linking keeps the context separate from your model and easy to update.
• DXF: use Insert → Import CAD with units set to metres and positioning origin to origin. In Revit 2024 and later, create a Toposolid from the imported contours (Massing & Site → Toposolid → Create from Import); in earlier versions create a Toposurface from the import instance.
• Placement: the IFC's map conversion describes UTM coordinates. How Revit applies it depends on the version and on how your project's shared coordinates are set up, so check the position against the survey point after linking.

ArchiCAD

• IFC: open or merge the IFC file; the terrain comes in as a mesh-like element and buildings as context masses.
• DXF: use File → Interoperability → Merge with the 2D DXF and choose metres. Then trace the contours with the Mesh tool, or use the contours as a reference for your own site model.

Rhino, SketchUp and Blender

For modelling and visualisation, OBJ is usually simpler than IFC: choose Z-up for Rhino and SketchUp and Y-up for Blender. Rhino also opens the 2D DXF with every contour at its height.

Limits to keep in mind

• The terrain is only as fine as the source data: about 30 m in most of the world, finer where national models are open. It shows the shape of the land, not kerbs or retaining walls.
• Context buildings are extrusions of OpenStreetMap footprints, with mapped heights where they exist and a default height elsewhere.
• For the plot itself, replace the exported terrain with a survey before design development.