I have recently been asked by a client for the ability to compare different versions of the same model. When I was asked to do this I scratched my head ans said “Oookkk” not really know why and how I was going to do this.
When I started this I asked myself, why would we want to compare models?
-To show the power of BIM. (vague but an answer)
-To see what objects had been deleted in the model (getting a little more to the point)
-To see what objects had changed in the model (getting a little more to the point)
-To see what objects were new in the model (getting a little more to the point)
-To see if the model is following the office standards (Using compare to help with model QC, hmm)
In my research I came across this article written by David light. In this article he wrote back in 2009 he explained different ways to compare models. David talked about using the Autodesk Revit Model Compare add in tool, as well as using Autodesk’s Design Review, and using Adobe Acrobat. Even though the article was written about 6 years ago it is still applicable today in 2015, but now there are a few more process as well. Today we can use Navis Works to compare models. See Navis works link to see how to do it. The Cad Technology Center (CTC) has a model compare tool which I recently talked a little about. CTC Revit Express Tools:Model Compare
Using Autodesk Design Review, Adobe Acrobat Pro, and or Blue Beam Revu all works the same way. These programs really aren’t comparing models they are comparing two different 2d documents. Don’t think I’m belittling this at all. Comparing the 2d information is extremely import. Having a program highlight and show you what has changed between different versions of the same documents saves a lot of time in finding the changes, good or bad.
CTC’s Model Compare and the Autodesk Model Compare tools are similar in how they work. Both programs look at the databases of multiple models and look for items that are different. CTC’s Model Compare takes a snapshot of the Revit Data base and puts it into a small XML like file, while Autodesk’s Model Compare requires you to open both version of the model to compare the models. Both the CTC and Autodesk Model Compare addin’s create reports that can be brought into Excel. These data centric reports have a lot of information, and generally a lot more information than I would generally use.
Within Navisworks there are two workflows to compare the models. The first method is to use the model compare function within Navis works that works like comparing 2d PDF’s,see this Navis works link to see how to do it.. The other method is to overlay multiple models on top of one anther. One of the benefits of Navis works is that you can insert multiple files into the same Navis works project. This functionality allows you to insert different version of a model and overlay the models to see the difference graphically. One the different models are in the Navis works project you can change the color of an entire inserted model, not just individual modeled objects. This workflow of overlaying the models I got from one of the engineers I work with at Bridger & Paxton consulting Engineers, who knows Navis works a hole heck of a lot better then I do. Reference Model Compare by Mathew Miller.
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