Please share your DWG/DXF import tips

[Howard leslie]

Edson,
Some Top Tips for importing dwg / dxf into SketchUp.
.......
If you have Autocad........

1. If you are importing a 2d CAD file, run the FLATTEN command - this ENSURES everything is actually 2d.
2. Run OVERKILL command - gets rid of any duplicate data
   (These 2 Commands are possibly Express Tool Commands).
3. Run PURGE command (most important Tip of the lot). Run PURGE again just to make sure !!! (PURGE ALL)

If you don't have Autocad, get the person who is sending you the file to do these 3 things.
..........
Hope this Helps
Bye
Howard L'

[thomthom]

1. In AutoCAD, copy what you want to import to SketchUp to a new file. This avoids many import issues it seems - seems like old DWG files can contain so much stale data that you get more junk in SketchUp.
2. Place everything around Origin
3. Zoom extent - to ensure there is no stray objects far off
4. Flip to a side view and check if some lines go up/down in an extreme distance. (I often come across drawings where lines shoot 50km into the air )
5. Explode Polylines and 2dPolylines (If a polyline contains Arcs SketchUp will import them as straight lines from start to end)
6. If drawing should be 2D, flatten to ensure it is.
7. Purge All

@edson said:

i never use the CAD lines: i draw over them. but, before doing that I move all that has been imported to one single layer and delete the layers that came with the CAD import. and, as soon as I can, I delete the CAD lines and purge my skp file, as CAD imports turn the skp file too heavy.

I find even drawing over can cause problems, as you can still inherit some tiny fraction of inaccuracy - like slightly off angle that just mess up everything later on. If anything, I try to draw with the rectangle tool as much as possible to ensure proper 90 degrees angles.

I often turn on Edges Color by Axis after importing to spot lines that are off axis.

[Gaieus]

@thomthom said:

I find even drawing over can cause problems, as you can still inherit some tiny fraction of inaccuracy - like slightly off angle that just mess up everything later on. If anything, I try to draw with the rectangle tool as much as possible to ensure proper 90 degrees angles.

I may not work with as many cad drawings as you guys (architects) but have learned this lesson already.

[thomthom]

@gaieus said:

@thomthom said:

I find even drawing over can cause problems, as you can still inherit some tiny fraction of inaccuracy - like slightly off angle that just mess up everything later on. If anything, I try to draw with the rectangle tool as much as possible to ensure proper 90 degrees angles.

I may not work with as many cad drawings as you guys (architects) but have learned this lesson already.

It's dreadful when inaccuracy creeps into the model - it spreads like the plague. You'll find that when you split a face overlapping faces are generated. Push-pull won't work because things aren't perpendicular or parallel - even though Colour By Axis indicate so .
I've re-modelled many models just because of this - I wasted more time trying to work with it as oppose to just rebuild cleanly.

[pbacot]

@thomthom said:

I find even drawing over can cause problems, as you can still inherit some tiny fraction of inaccuracy - like slightly off angle that just mess up everything later on. If anything, I try to draw with the rectangle tool as much as possible to ensure proper 90 degrees angles.

I often turn on Edges Color by Axis after importing to spot lines that are off axis.

Well, what would be the point of the import? My drawings aren't THAT bad, but then, I don't use AutoCAD . But yes and to rectangle drawing and starting (and checking) models with color by axis.

... Peter

[dale]

One of the things I do before every import is make sure the camera is in parallel projection, top view. I can't explain why, but this has really helped to assure there are less problems down the line.
Since quite often I am receiving AutoCad drawings from others, I think I will compile a list from suggestions here and send it to the exporter as a to-do list before sending me the file.

I have also noted less problems with exports from other Cad software ie: Vectorworks, Softplan.
Edson, this is a great idea for a thread.

[andybot]

Here's a flatten command (that I use very successfully) for using in ACAD LT. This is because flatten and overkill are available only in full ACAD.

http://www.cadtutor.net/forum/showthread.php?20684-Z-Co-ordinate-Flatten-command

[Edson]

there are same very useful tips here: Flatten Crappy CAD Drawings.

[pbacot]

In that video Edson, the nugget is the idea (after import) to re-export a parallel projection overhead view to dwg from your SU file, then re-import into a new SU file, in order to flatten it. Something I have not heard suggested before.

[mitcorb]

If you use autotoilet at all, you should use the snap functions. But, just because you can preset automatic snap to intersection, endpoint, midpoint, apparent intersection, and so on, having too many of these running is where the problem arises. There are instances where you may be in a hurry, and clicking just so, will confuse the program. It will send a vector off into either Z+ or Z-, but look like it connected with the target, and the problem becomes cumulative.
In the 2007 and up versions there is a properties side window, by which you can modify a lot of values. Doing a box select without an initial command will display the grips. Expanding the properties side window will allow you to step through the entities types to verify their start and end values, their z values and so on. You can overwrite or edit in some of the fields.--Just another method.