IMPORTING 2D CAD FILES

Sometimes the only information available is as CAD files.

CAD files can be brought in to Revit and used as reference or even appear on finished drawings.

However CAD files will SLOW Revit down. They often contain an enormous amount of lines that all have to be displayed.

In Revit 2D is NOT simpler and quicker, only use CAD files when absolutely necessary.

2D CAD files may be imported:

• as 2D survey

• as background information - existing conditions, consultant information

• to base modeling on, e.g. designs done in CAD.

Details done in CAD must be imported into a Detail Component family rather than straight in to a Revit project (see IMPORTING CAD DETAILS).

3D CAD files must be imported in to a family file rather than straight in to a Revit project (see IMPORTING 3D CAD).

PREPARING CAD FILES

It is best to make a copy of any CAD file to be imported.

Place the copy in a subfolder of the projects's Revit folders:

e.g.

....\Revit\LinkCAD\Site

Use a naming convention that identifies the original CAD file and its date.

General naming protocol:

PURPOSE_isodate(original CAD file Name)

or

PURPOSE_isodate(block from original CAD file Name)

e.g.

SURVEY_150317(9334-S-00-Feature-Re F & L-V3).dwg

SURVEY_141114(213008-XR-SURVEY from CV-01-350[J]).dwg

Clean up the CAD file by:

• Purge everything.

• Make sure it is set to WCS (or equivalent).

You could also make other changes, but only do so if you don't expect any CAD updates:

• Delete things not required.

• Rename layers important to you.

• Change layer colors important to you (remember colors are opposite in Revit).

• Add information important to you - e.g. True north, location of project base point, notes.

Don't waste too much time cleaning up CAD files unless they will be used for the whole life of your project.

Take note of the Units of the CAD file - you need this when you import in to Revit.

IMPORTING CAD FILES

Before importing CAD files make a decision as to whether the CAD file should be in a separate linked Revit file rather than the main project file.
CAD files bring in a lot of rubbish - materials, line patterns, etc. that clutter up Revit. By putting CAD files in a linked file this can be avoided.
If the information is static - like a Survey - it is best in a separate linked Revit file.
Placing CAD files in separate linked Revit files is the same process as below, plus some extra steps described further below.

It is important to take note of the Orientation of the view you are placing a CAD file.
Revit remembers which orientation - Project North or True North - was set in the view when the CAD file was placed.
If the orientation is changed from that original value, when the CAD file is Reloaded it will rotate itself.
And it is only the original view that matters. Changing orientation of other views where the CAD file is visible makes no difference.
(To fix a rotated view change the orientation of the view the CAD was originally placed in back to its original orientation and Reload again.)
Because of this it is best to place a CAD file in a view that is unlikely to have its orientation changed.

Or better still create a working view just for placing 3D CAD files so you know which view has been used for placing CAD files.

After preparing the CAD file in Revit create or go to the view where you want to see the CAD file.

Use the Insert > Link CAD command.

1. Browse to and select the CAD file.

2. Tick Current View only
   (otherwise the CAD file will be visible in every view, including elevations and sections. Use copy and paste to put it in other views.
   It also makes everything in the CAD file 2D)

3. Invert colours
   (generally a good idea as CAD files have black backgrounds).

4. Bring in All Layers/Levels, frozen layers will come in turned off.

5. If you know the CAD file's units select them
   (Revit isn't always successful at guessing)

6. Untick Correct lines that are slightly off axis, particularly if it is a survey.

7. Change Positioning to Auto - Center to Center
   (NEVER use Origin to Origin. CAD files usually have insert points many hundreds of kilometers away).

The CAD file will come in at roughly the center of your current view.
You may not see it because by default CAD files are put in the background, behind the Revit model.
To bring the CAD file forward select it. If you can't find it select using a crossing window (top right to bottom left), then use Filter to untick everything but the CAD file.

Once selected change the Draw Layer parameter of the CAD file to Foreground.

You can also do this from the Option bar.

Next move and rotate the CAD file to place it correctly in relation to your Revit project.
Keep in mind the world revolves around Revit. We do not use CAD files to locate our building within Revit, we use our building in Revit to locate the world around it.

If you want the CAD file in other views, select it, Copyclip (Ctrl C) it, go to the other view, and Paste Align to View.

If you don't know the names of layers you can use the Query command, then select a CAD object:

A dialog box appears telling you things about the object.

There are also buttons to Hide in View or Delete the Layer (or Level).
Note that deleting a layer means the objects on it are gone forever, if you hide the layer you can bring them back.

VISIBILITY/GRAPHICS OVERRIDES

Another way to control layers of levels is using Visibility/Graphic Overrides.

In the Visibility/Graphic Overrides dialog box go to the Imported Categories tab.
You can hide whole CAD files by unticking them.

Click on the plus symbol to see all the layers in a CAD file.

These can be hidden by unticking them.
You can also Override their graphic settings to change their pen weight, color and line style.
These settings will remain if the CAD file is updated (as long as layers names stay the same).

Open the main Project file and link the Revit file containing the CAD files.

In views where you want the CAD file to be visible use Visibility/Graphic Overrides to control visibility.
In the Visibility/Graphic Overrides dialog box go to the Revit Links tab.
Under Display Settings change the Revit link to Custom.

In the next dialog box under the Basics tab hit Custom radio button,

Opposite Linked View: change it to the view you created in the linked file.

Next go to Import Categories tab change Import categories to <Custom>,

Make sure Show import categories in this view is ticked.

Note you could change visibility and overrides in this dialog. However it is better practice to use one of the views you set up in the linked file instead.

Hit OK and finish.

These settings can be captured in a View Template and applied to other views.