Navisworks Clash Detection 101 – Part #1

Part #1 – The Clash Detective Window

To the average engineer or modeller, Navisworks and clash detection go hand in hand, some people think that they are one and the same. If you’re not familiar with the terminology, clash detection is a process that identifies interference between elements in your model where as Navisworks is an Autodesk product that facilitates automated detection of the interferences between modelled elements. These interferences, or clashes may be between different models or within the same model, they could be between disciplines or within the same discipline.

The concept behind clash detection during the design process is that you can identify and fix problems before construction begins, therefore saving time and money down the track. Provided that it is configured correctly, Navisworks can help to speed up the process and reduce human error during model inspection by running automated clash reports.

The problem with Navisworks however is not everyone knows how to use it effectively. Maybe you’ve been to training with a reseller in the past and you walked out the door still scratching your head. After spending a whole day working on 4D timelining, 3 hours showing you how to animate an automatic door in Simulate and less than an hour spent learning the very basics of clash detection in Manage or maybe you’ve had no training at all? Either way you’re only just barely making your way through your clash detection sessions.

Over my next few articles I will outline a few of the clash detection basics to get you more confident in your adventures into clash detection, I’m not going to claim to solve all your clash detection woes, but whatever your experience, it’s always good to have something to refer back to.

In this first installment, I’ll explain each of the parts of the Clash Detective interface.

The Clash Detective window allows you to specify rules and options for undertaking clash tests. In this window you can view results and generate clash reports.
The Test Panel is where you will find all of your clash tests. The test panel isn’t displayed by default, you need to click on the Add Test button in the clash detective. When you select the Add Test button, a new clash test will be created and added to the test panel.
Under the Rules tab, you can define rules in which Navisworks will use to ignore clashes, by default there are four pre-defined rules shown under the rules tab.
In the lower half of the clash detective window we have a section with a few tabs, the Select tab is the default view in the clash detective window. In this tab you can define the clash test by selecting multiple sets of items at a time. You could clash a whole model against a whole model, however this would be a very inefficient process, instead you can test clashes between different selection sets of elements in the model.

The Selection A and Selection B areas display all the items in a hierarchical list that replicates the selection tree window. You can select objects from these areas that will be tested against each other during a clash test.

Beneath the selection windows are a group of buttons which allow you to change what geometry is clashed in the test.

2014-11-29_7-59-59 When Surfaces is selected, surface geometry is included in the clash test. Surfaces is selected by default when you create a new clash test.
2014-11-29_8-00-15 When Lines is selected, line geometry is included in the clash test.
2014-11-29_8-00-28 When Points is selected, point geometry is included in the clash test
2014-11-29_8-08-55 Self Intersect is used to test the selected object against itself for clashes
2014-11-29_8-09-18 The Use Current Selection button is used to select objects directly in the scene view for clash tests
2014-11-29_8-09-31 The Select in Scene button is used to highlight the elements selected in the clash test. They will appear in blue when selected.


The Results tab is where you view the clash results. This tab is divided into three parts, the Results pane, Display Settings panel and the Items panel. By default the Display Settings and Items panels are hidden. They can be accessed by clicking on the panel title which is highlighted in the image.

The Results area displays a list of clash results in a tabbed format showing the name of the clash, the clash status, the date found and the description of the clash. If the clashes have a saved viewpoint, then the viewpoint icon will be displayed in the viewpoint column as well.

After expanding the Display Settings panel, you are provided with options to change which clash is highlighted, choose not to highlight the clashes at all, dim the other elements within the model so you only see those that are related to the particular clash as well as adjust basic viewpoint and simulation settings. 
Hidden at the bottom of the results tab is the Items panel. Once expanded you can view information on the clashing objects. The clash information displayed will depend on the select clash configuration.
Finally, in the Report tab you can adjust options for generating clash reports. The generated report will contain the details of all the clash results for the selected test. The report tab has three sections; Contents, Include Clashes and Output Settings.

In the Contents section, you can select the contents of the report, such as the date found, item numbers, grid locations, coordinates of the clash among others.

The Include Clashes section allows you to filter by new, active, reviewed, approved or resolved clashes.

The Output Settings section allows you to select the output format of your clash reports. It allows you to select either the reports from the current clash test or from all clash tests either as a combined or separated format. You can also choose from HTML, XML or recorded viewpoints as your clash report format.

In the next installment, I’ll build on what I’ve shown today and explain how to create selection sets to get better results from your clash tests.

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