Grouping clash results

In any given building model, there is a number of issues to be addressed. A large part of these issues are what we call “hard clashes”, when a building component physically penetrate the space occupied by another building component. In these case, two or more building elements compete for the same volume.

Finding these clashes is now quite simple thanks to clash detection software that detect geometrical interferences between elements of a building model.

But after having a hard time finding these issues through coordination sections hand-drawn from plans, we now face the inverse problem and end up with too many clashes in our models. Running a simple clash detection can quickly yield thousands of clashes, making the entire process nearly useless.

Furthermore, a clash only represent a geometrical intersection between two elements, and is more a part of an issue than the issue itself. We have to group these clashes to be able to extract meaningful issues from the meaningless clashes.

Grouping these clashes is generally a manual task, and the user have to run through thousands of clashes to sort them in relevant groups.

While trying to automate this tedious task, I run across the examples provided as part of the Autodesk Navisworks Software Development Kit. These examples include a nice Clash Grouper plugin for Navisworks, enabling various method for grouping clash results.


As an example, I run a clash detection between the blue Selection A and the green Selection B, and get seven clashes, shown here as red dot:


With the Clash Grouper, I can group these clashes by grid intersection:


I can also group them by cluster analysis, where we search for the optimum grouping solution given the expected number of groups:


I also add my own method for grouping clash against a specific set. I use this to group all clash belonging to a single element in one of the two selection sets.


Here, I group by element from the Selection A (blue)


Here, I group by elements from the selection B (green)


If elements from one set are more relevant for the end user, the final clash report is clearer for this user when clashes are grouped against this set.

This plug-in enables a lot of possibilities for sorting clash detection results in a meaningful report, and will become a full-time member of my coordination toolbox.

To install this plug-in, you can copy-paste the ClashDetective.ADSK.dll file available here in a new ClashDetective.ADSK folder in C:\Program Files\Autodesk\Navisworks Manage 2016\Plugins. You can also see my edited version of the example code here.

35 thoughts on “Grouping clash results

  1. Nice find Simon.
    I was trying to add this to Manage 2015. Is that possible or is this taking advantage of new functionality that’s only in 2016?


    • Hello,

      The .dll I provide in this article only works with Manage 2016, but the code itself can be compiled with the 2015 version of Navisworks.

      • Hello, I am also trying to add this to Navisworks Manage 2015. I am a beginner programmer. Could you possibly explain all the steps I have to take to make this work in Navisworks Manage 2015?


  2. Simon, I am interested in this workflow, but after copying the .dll file to C:\Program Files\Autodesk\Navisworks Manage 2016\Plugins (Windows 7), I am unable to see it in Navisworks. I have both Service Pack 1 and 2 installed an no other plugins. Do you have some insight on why it would not be loading?

    • Never mind…I’m going to blame my lack of sleep for not reading carefully and creating a folder to put the file inside. I missed the part that says “in a new ClashDetective.ADSK folder”.

      I have it loaded and post my test workflow. Thanks for posting.


  3. I have the ClashDetective.ADSK.dll installed in my 2015 Navisworks but it is making my Navis crash as often as not. I have service pack 3 installed and it seems to crash more often when I use the Group Clash Results tab and choose by selection A. It is amazing when it works but it is crashing a lot also. Any thing that you know of to stop it from crashing my Navis?

  4. Hello,

    I am running navisworks manage 2016 and have downloaded and installed ClashDetective.ADSK.dll. It works great, except for the following, when I run a clash test and then use the grouping by element, it groups everything as you would expect, but also creates a group for any single clash. When I try to explode the groups with only 1 clash in them, navis crashes. Any thoughts or advice on how to fix this would be greatly appreciated.

    Thank you,

  5. Simon I was excited to see this plugin. i can not get it to work for Navisworks manage 2016. can you shed some light on what i am doing wrong? i followed all you steps and nothing. do i need the plugin that you described at the beginning of your artical first the “Clash Grouper plugin for Navisworks” ? If so i could not find it in the app store.

  6. Hello Simon, First thanks for your work seems really usefull! unfortunately i crash my navisworks each time i run the plugin (i have a 2016 Version) Could you please help me?

  7. Hey Simon.
    Great post, enjoyed your AU video as well!
    I used your modified version in Navisworks 2015 and it works perfectly. Now i have projects in Navisworks 2016 i used the 2016 version and it crashes every time, on every Navisworks file i try it on. Even simple clash tests where there are only 10 clashes. As soon as i run the Clash grouper (using any setting) it crashes Navisworks instantly.
    Do you have any advice?

  8. Pingback: Automatic Grouping of Clashes in Navisworks with Free Addin – What Revit Wants

  9. Hi,
    I am using Navisworks 2015 as i am doing group for clashes may i know where can u group clash page. i installed the ClashDetective.ADSK.dll file in the specified position.

    Please let me know
    Rakesh singh

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