Importing DWG files into SketchUp can lead to unexpected results and problems. In this guide I’ll outline the steps I perform when importing a DWG drawing. The DWG files I work with are usually building plans or site plans for architectural projects.
I avoid importing directly into SketchUp. A DWG file often contains excess old data which you don’t want to import and some features doesn’t translate well into SketchUp unless you make some preparations.
1. Copy all geometry to be imported to the clipboard.
2. Create a new DWG file.
3. Paste everything at the origin.
This is to avoid problems with old stale data and hidden stuff that might cause problems when importing into SketchUp.
4. Explode all 2D Polylines
Arcs within a 2D Polyline will appear straight when imported into SketchUp unless you explode the 2D Polyline so the arc segments are extracted from the polyline.
These are the final steps I perform in AutoCAD that I do in order to reduce the amount of stale data imported.
It might sound a bit convoluted but all these steps have specific purposes and have proved themselves over the last five years to greatly deduce the amount of problems that might appear when working with imported geometry.
8. Check DWG units.
Before closing the file I ensure to check what units are used in the DWG file as we need to know this when importing into SketchUp. In AutoCAD you can do this by typing the command:
Importing into SketchUp
9. Open a new SketchUp model.
I avoid importing directly into a working model. Instead I open a new fresh model so I can ensure the import is correct before merging with the main model.
10. File → Import → Select File
If you import with the incorrect units and simply scale up or down the geometry to fit you might run into accuracy problems.
Also ensure that “Preserve drawing origin” is unchecked. SketchUp doesn’t handle extremely large units very well – which is what you will get if you import a DWG which was drawn at world coordinates.
If you don’t do this you are likely to suffer from the mighty “clipping bug” where as you navigate around your model parts of it will appear to be clipped away and you start seeing through your model.
11. Remove all materials (Optional)
The DWG files I import often have colours applies to the edges. I very rarely have any use of these materials. Because of that I tend to remove all materials of the imported geometry.
Instead of removing each material one by one in the Material Browser I use a plugin I wrote, Material Tools, which will do it in one big schwoop! Another reason to import into an empty file and not your working model.
12. Window → Model Info → Statistics → Purge Unused
Notice I have checked the “Show nested components” checkbox. It does not affect the purge operation, but it makes the statistics display information for the whole model, not just the root level of the model.
13. Inspect the model and see if everything looks OK.
You might find that some blocks, imported as components, will appear to jitter and jump around in the drawing when you navigate the model. The reason for that will be that the block had an insertion point far away from the geometry. You can either explode the troublesome components, or if you need to keep them as components you can simply reset their origin. You can use the plugin Axes Tools to reset the axes en masse.
Additionally, Dynamic Blocks in AutoCAD might cause unexpected results when importing. For instance, at the office we sometimes have a dynamic block for vehicles with different turning radiuses illustrated. This dynamic block has multiple blocks inside it which is hidden depending on which radius you want to display. When these are imported into SketchUp all the variations, all the hidden blocks, inside the dynamic block will be visible. These require cleanups either in AutoCAD or SketchUp – removing the redundant hidden blocks.
Note on DWGs with 3D data
If you’re importing DWG files with 3D mesh data you might want to run CleanUp on it after step 11. This will attempt to reduce excess edges and faces which can greatly increase the performance.
Bonus Tip: Exporting
When you export a DWG from SketchUp the units will incorrectly be set to inches. Example; if you export a 1000×1000 mm square it will be 1000×1000 units in the DWG, it will be set as 1000×1000 inches.
To correct this you must redefine the unit type in the DWG file. In AutoCAD, type
UNITS and you should get a dialogue where you can change the units.