I'm glad to see this topic gained some traction... (I've noticed it only now, I still forget to subscribe to topics)
Yesterday I discovered a handy feature of civil3d (I don't use it directly, but my colleagues do) that allows to create a terrain surface starting from an .ASC file in 2 simple clicks (one for importing the surface points, the other to create the actual surface). Then I thought that FreeCAD could use some QGIS/GDAL/GRASS power (Also yesterday another colleague asked me if I knew a way to translate a kml file into another projection and put it in autocad and I pointed him to QGIS). Not sure how it can be done (and if we need all the features of qgis).
I'm at home and don't have access to civil3D, but I can offer you some more information:
- here's a video showing the basics of alignments: https://www.youtube.com/watch?v=hQehH-rid_s
- after creating the alignment we want to get the profile of the terrain and subsurfaces (or volumes), if they exists
- another step is to create the profile of our infrastructure (road or tunnel) and convert it to a 3d polyline
- also we could have the need to do the inverse process, from 3d polyline to alignment + profile, and from alignment+profiles to surfaces (as stated in my previous post)
- given the cross section of the road/tunnel, place it along the alignment (at some point it can change) to have a 3d representation (and also get 2d views/drawings) of the infrastructure and the volume of earthworks needed (if geological subsurfaces are present, the volume should be divided by strata)
- There's an open standard called landXML, that could be used for data exchange (used also by civil3D)