So continuing with my last question (Create 3D dxf with OGR) I have decided to give the GRASS option a go.
I have imported my polylines into GRASS using v.in.ogr and converted them to 3D using v.to.3d. I checked the lines using the GRASS info tool and the polylines all have the correct z values. I then exported it using v.out.dxf but this is where I am having troubles.
The dxf contains the z values for the polylines:
VERTEX 8 line 10 401120.708496 20 6875185.007069 30 539.000000 0
However when I open it in AutoCAD Civil 3D it doesn't recognize the z value and just makes all the lines 2D. I have checked them with the info tool in AutoCAD but the z values are all the same.
Is the dxf created using v.out.dxf supported in AutoCAD in order to get correct 3D?