Default Rule Clarification

[RevitNinja]

I've got a Revit model containing a few light fixture families. I've brought this into NW and predictably, Clash Detective is picking up the fact that one particular light fixture is made up of multiple composite parts. Nothing I didn't expect.

I noticed on the Rules tab that there is a default rule called "Items in previously found pair of composite objects." Re-running the test with this rule engaged eliminated 6 extra clashes - the ones that were caused by the composite objects. This is a good thing and is exactly what I was looking for...

Then I repeated the whole process from scratch. Exported the model from Revit again, created a new nwc, etc. I ran the first clash test with this rule checked and I noticed the results were the same - 2 legitimate clashes.

What I don't understand here is that the Help file claims that this rule affects composite objects picked up in a previous clash test. If there was no previous clash test (first run on a brand new file), how does it function?

[pauljordan]

I've never seen where a rule works on previous clash test results.

When I run rules, I bring them in from the beginning and run my clash report. If I run it a second, third, one hundreth time, the results will be the same..

Now, if I run it like you did, THEN invoke the rule, yes, the numbers will be different if the rule is pointing to something it can exclude.

Try going through the steps where you recreated the model again. But, before you run the clash test, take a look at those rules. The reason I say this is because the rules file is a system file, not one that follows the model 'except' if you send it to someone that doesn't have any rules setup on his/her computer.

It's also not a file you can edit from outside of NW.. (GRRRRrrr I'd SO love to be able to alphabetically sort my rules... Just try finding the status of that one simple rule with you have 85 of them and 65 clash reports.)

What I think you'll find is the rule is already selected based on it's status the last time you worked in NW.. So, when you selected the rule, then started a new model, imported your revit.nwc file, then ran your report, the rule was more than likely selected.

Rules are insane to work with at times.. But, they don't hold a candle to creating selection sets..

[RevitNinja]

Thanks for the reply, Paul. I was under the impression that the rules were file-level and not system-level. Most everything I do in NW is run via search sets. I work exclusively with Revit, which I thought would make things easier, but optimizing NW workflow just for that platform has been challenging.

Do you have any recommendations on getting Clash Detective to ignore the composite parts and just picking up the whole item? I already toggled the "Collapse on Convert" setting. That helped, but not entirely...

[pauljordan]

That's where selection sets would help RN.. You need to find a common denominator in all the parts you want to exclude, then make a selection set, then make a rule. Always remember those 3 important rules at the top of the Clash Detective Rules tab... Ignore Objects Between..

Selection sets are definitely a challenge and you have to kind of backwards think them at some times to get the output you want but, when they work, they work great..