Forums >> Revit Building >> Technical Support >> Lineweights in Revit to CAD Export

kittyj2345

active

Joined: Fri, Jul 17, 2015
0 Posts
No Rating

Working in Revit LT 2014.

Our office is trying to figure out how to export from Revit to AutoCAD (also 2014) and have a DWG that will print correctly without needing to modify graphics in AutoCAD. The best workflow I can figure out is to export from Revit using "Export category properties BYLAYER and overrides BYENTITY" and then plot from AutoCAD using a ctb file that prints using the object's lineweight setting rather than color. Theoretically, with this workflow I should be able to export a sheet to AutoCAD, plot it, and have it look exactly the same as a plot directly from Revit. (Right?)

I did that, and they are not the same (see two attachments). The differences I notice immediately are not lineweights, but color of fills: the walls, scale bar, and filled regions in title block are all darker in the AutoCAD version than they are in the version exported directly from Revit. Why would the graphic properties of those objects not be translated to AutoCAD properly?

Also, if you know a better way to approach this workflow, I'd love to hear about it!

This user is offline

WWHub

site moderator|||

Joined: Tue, May 16, 2006
13079 Posts

Getting an exact match is almost impossible.  I would not do what you propose. 

Several factors here.  First and foremost is that Revit's lineweights are dynamic and driven by view scale.   That in itself will give you problems.  Run this very simple test:

1. Floor plan view - short wall that has multiple layers with one being brick
2. Set the view to fine 1/8" scale
3. Copy the view and set to 1/4" scale
4. Copy the view and set to 1/2" scale
5. Copy the view and set to 1" scale
6. Place all views in sequence on a blank sheet
7. Export normal bylayer overrides by entity.
8. Now inspect the lineweights

For me in Revit, my cut lineweight for walls is 7.  A 7 @ 1/8" scale is .026" (0.6604)   In CAD, that line says .53mm

In 1" view, that line in Revit is .0276" (0.70104 mm) In CAD that line says 7mm

Hatch patterns in Revit are typically pen 1 - .0030" in CAD they become .09mm (0.00354331")

So there are conversion problems here.

ALSO _ USE THE PCP FILE THAT REVIT PROVIDES instead of the ctb file.  It will get you closer.

This user is offline

kittyj2345

active

Joined: Fri, Jul 17, 2015
0 Posts
No Rating

I understand Revit's lineweights being dynamic could be a problem, but would it be a problem if we stick to the same scale that is exported? For example, we export a sheet at 1/8" scale, make some changes in CAD, and ultimately print a drawing that is still at 1/8"?

Anyway, the lineweights themselves are working okay for me- they aren't perfect, but the relationships between lineweights are matching our intent. What is not matching our intent is the color of fills, as I mentioned. 

Plotting with a ctb created from the PCP file isn't working, either. From looking at the ctb file, it looks like Revit automatically generates lineweights for this file that match the settings in the Revit drawings, but there isn't a % screening for any of the colors in the ctb file, so everything prints black. This method is actually a bit worse than printing with the object type properties. 

I gather that it would just be better to avoid this workflow of exporting from Revit to AutoCAD and then printing from CAD, but the people who make decisions about our workflow want to be able to do it this way. 

This user is offline

archigrafix

active

Joined: Fri, Jul 5, 2013
38 Posts

Regarding precision and consistency in linetypes. Those interested in ISO linetypes that are correct in all scales and thicknesses, should have a look in this webpage:

http://www.archigrafix.com/technical-lines-iso-128-20.html

-----------------------------------

Marc Faber

BIM Solutions Developer

goto.archi | Oslo, Norway

This user is offline

View Website

lauraperezmestre

active

Joined: Wed, Aug 9, 2017
0 Posts
No Rating

OP did you find a way to do this? Im facing the exact same problem and have created several ctb files to try to match the revit exports but with no success. This happens specially with the elevations. Maybe will have to create separate ctb files for plans and elevations. Using the pcp is fruitless and the people in charge refuse to plot from PDF.

Please tell me you found a workaround, im desperate...

This user is offline

Linked Cad File - Lineweights

2

Lineweights from CAD to Revit

5

Revit to CAD then use current cad layer standard, how?

1

Export to CAD - Colors

4

imported dwg lineweights, linetypes

1