Importing Surfaces or NURBS from AutoCAD. (workaround)

Tutorials
#1

Do you have a really nice curved surface or NURB in your AutoCAD model and you want it into SketchUP?
If you try to import a NURB in to SU, you get a few lines at the most. In AutoCAD you can’t convert NURBS or Surfaces to Meshes or something usable in SU, to my knowledge…
The next procedure is workable, if you got just one or two NURBS you really, really want to import.

Here is what to do:

  • copy the NURB or Surface to a new drawing and maybe trim it so you get all the curves right. (see picture)
  • explode the NURB.
  • Now you got some splines.
  • Check if all edges touch on a endpoint of the other edges.
  • break them in 4 pieces.
  • (check SURFTAB1 and SURFTAB2 if they are high enough)
  • Use command ‘EDGESURF’ and select the 4 splines.
  • If all splines meet, you’ll get a nice MESH.
    Attention!: It may not be so well curved as the NURB, but it’s better than nothing…
  • Now select it and type ‘Explode’. (x)
  • Then just save it as a DWG. (if you got SU Pro.)
  • In SU choose ‘Import’ and load this DWG.

nurb2mesh.jpg2214×1218 320 KB

And there you have it! :slight_smile:
Select the object and adjust the Smoothing to get a nice surface.
Again,this is workable if you got just a few surfaces.
If someone knows a better way, I really would like to hear it!

BenS.

#2

As AutoCad no longer exports to 3DS, I found that exporting to STL and importing that into SketchUp also does a version of this trick, at least for solids with NURBS geometry.

Anssi

#3

Hello Anssi, thanks for the response, (sorry for my English)
I have tried STL, but it doesn’t export Surfaces. It will only export solids…
How do you import STL in SU? I don’t see this extension in Import or Open?

BTW: I suppose you know that you could use 3Dsout through ARX files untill AutoCAD 2008?

BenS.

#4

STL export and import can be done with a free plugin created by the SketchUp developers. It can be downloaded and installed from the Extension Warehouse.

Yes, in the old days I often used the 3DS format but today I don’t have access to that old AutoCad versions. 3DS also has severe limitations (old DOS file naming and the about 64000 triangles limit per model come to mind).

Anssi