2021 Navisworks clash distances (severity or magnitude) does not seem to make sense too much often

Hi,

We noted some pretty concerning issues with the clash tool in Navisworks. We first noted that several clashes were missed by the tool if set on Hard Clash instead of Conservative, and we were also wondering how the tool claculates the clash distances (or severity, or magnitude). After searching and reading a lot on the web, we finally got a pretty clear explanation here

(moderator note: the forum software prevents links for the first few posts ... see links in following post - CAtDiva)

The most important would be the third link where it is stated the following

"Clash Detective will report the minimum distance one of the objects will need to move so the Clash no longer exists."

So it makes sense that hard method sometimes does not pick up clashes because these are close to the triangular mesh limit and therefore within the set tolerances, while the conservative method consider the whole object... Also, the shortest path possible along through the object must be moved to clear the clash should be the clash reported "distance". Great, except that it's not!

We run some test in Navisworks 2021, using 2 NWC model exported from Revit. We run two separate clash test with the same settings, tolerances and selections with the exception of the clash method, one Hard the other conservative. Then, we look for clashes detected in the conservative test that haven't been detected in the hard test, to check if it was actually clashes close to the triangular mesh limits. Well, most of those clashes detective in conservative should have been picked up in hard clash as well, and were not! Moreover, distances on several of them didn't clearly correspond to the minimum path to clear the way.

I was thinking to share some screenshot or even the file, but it's hard to see the issue in a picture... I was wondering if anybody ever run some test or verifications on this matter: do you guys trust the clash detection tool in Navisworks and the distance parameter? Because I'm starting having doubts...

Regards,