3D DWG into SketchUp Conversion Workflow

dwg
conversion
cad
import
autocad

#1

I am currently working with a 3D DWG file trying to get it into SketchUp but I am running into some problems. I’m not familiar with AutoCAD’s 3D features so I am hoping someone can enlighten me.

The DWG I was given has many curved surfaces with some flat edges. The flat edges come through after I explode each block, but the curved surface does not (left object in both screenshots). I am able to convert that surface to a mesh and explode it in order to get something into SketchUp (right object in both screenshots). However as you can see this breaks the curve of the surface and creates a pretty big gap. Obviously to some degree that curve will be segmented coming into SketchUp, but is there a better way so it’s minor or matches the segmentation of the flat objects?


Not really knowing the differences between 3D cad objects, the only thing I’ve been able to determine with any certainty is that SketchUp does not like Regions. My flat Surfaces import fine, but not the curved one. An unexploded Mesh does not import, but an exploded one does.

In theory I could use CAD’s 3ds exporter but I will quickly hit the face limit in the original model, and I would prefer to avoid copying out and reassembling each piece individually. Exporting to FBX also does not produce anything usable.

What’s the best way to convert the file? Any tips are appreciated!


#2

The problem is that the DWG importer in SketchUp doesn’t support 3D geometry that is based on splines (NURBS) so for the import to be successful, you must either use only polylines to generate the surfaces or solids, or, as you have done, explode them before importing.

Another thing that causes missing faces when importing is very small geometry. That can be helped by using a larger import unit than the original CAD modelling unit, and then to scale the resulting SketchUp model back down.

To get good answers in the forum it helps if you can upload a small DWG file that causes you problems so that others can test it.

Anssi


#3

Thanks, here’s that piece.

Surface vs Mesh.dwg (187.3 KB)

It’s definitely not a scale issue sadly, as I accidentally imported it into SketchUp at 1000x the correct size.

I have no idea how they were originally built since it is someone else’s file, unfortunately, so I am just left with trying to get the extant surfaces into SketchUp as they are.


#4

SketchUp User Guide


#5

Thanks, unfortunately I don’t think those go into enough detail for the problem I’m looking at. The supported elements page does show, for example, that Regions aren’t supported, but doesn’t mention Meshes or Surfaces. Unfortunately all my CAD knowledge is 2D so I’m kind of at a loss.

I believe (going from everything I’ve read/tested so far) that exploding a Mesh makes it into 3dfaces, which SketchUp can read, but I have no idea why for example the Mesh conversion is so different than the Surface or why how to make the curved Surface readable to SketchUp (I’m assuming convert the curves somehow since that is one thing SketchUp doesn’t do).


#6

The page seems really, really old and ought to be updated. It doesn’t mention solids either (as with Surfaces, some of these work, others don’t), or polyfaces (the entity type that most closely resembles SketchUp faces).

The age of the page shows in the mention of ADT (Autodesk Architectural Desktop). The product was renamed AutoCad Architecture (ACA) about 10 years ago.

Anssi


#7

Thanks, I’ll do some internet sleuthing on polyfaces! And I’ll reach out to tech support and see if they have any advice.

I’ll be sure to report back with any new info.


#8

FYI, Annsi has opened a new issue thread in the Meta > Help Center Issues sub-category:


#9

Thanks! :slight_smile: I will keep my eyes on that as well.


#10

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