By Garry Stockton
Whilst many people look at Navisworks as a Collaboration, Communication and Clash detection tool, using the compare functionality is never thought of. This is a great way to compare the changes made in any model.
The first thing you need to do is Export the models from Revit. There are a few different file types that you can export. Navisworks can read the Revit file format, but I wouldn't use that format in all cases, really in very few cases actually. When trying to compare different versions of the same building I would actually export my Revit file as a NWC (then convert to NWD) or DWF file. The reason I would export it as a DWF file is because DWF's are small files and multiple versions can easily be stored, also these files can easily be imported into Navisworks.
Next we import the files into Navisworks. We do this because the files are usually made from the same file, their origins are the same so they will come in at the same point, on top of one another. You import the 2nd model by clicking the append button (1), then select the two files you want to compare (2) in your selection tree.
Staying on the Home tab, go to the Tools panel and select the Compare. Note that the compare tool is greyed out until you select 2 items you want to do the comparison on.
Once you have selected the item for compare, a dialog box gives you options to choose for the compare, so you could choose whether it's looking for differences in the geometry or just in the properties. Then for the results you could hide matched elements and highlight differences.
Make sure you note that the Overridden Material and Overridden Transform check boxes relate to changing the colour and transparency in Navisworks, and changing a file's origin, scale or rotation since loading into Navisworks, respectively. These check boxes are clear by default, and all the other criteria relate to the properties of items from the original model.
The compare function then creates the two models’ in different colours so that you can see the changes in the two models. In this Project red highlights where changes have been made.