Forums >> Revit Structure >> Technical Support >> AAARRRGGGHH! Joist questions!

BigD

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Joined: Mon, Nov 26, 2007
100 Posts

Answer to first question: VISIBILITY PARAMETER (which is a yes/no type parameter).  You MUST learn how to use these because they're of infinate worth in creating/modifying families.  And they're really simple once you get the hang of it.

Answer to second question: I'm not really sure if we're the only ones or not.  i haven't really looked.  Somehow or another, I've gotten by without this function (for the most part) for the past 5 or 6 years or so that I've been in RSTRUC.  I have tackled it in specific situations but I think I just kinda did a "work-around" solution rather than really taking the time to develop a joist family that works for everything (flexible).

It's very much worth your time though to go ahead and figure it out.  Not only will you have a really nice family when you're done, but you'll have learned a LOT.

Don't give up!

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seniorcad143

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Joined: Fri, Oct 2, 2009
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OK - now i drew in four symbolic line like you suggested and I labeled each one of them as a parameter.  (below are the parameters in the "Other" category - but what is the box with the check mark in the value category?  I checked my books and can not find it)

Now all I need to do is figure out how to write the formula for each line.  Every time I try one it comes up with a message that I can not do it.

I will keep trying.

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Yeesh - Where is My Cad

Yeesh - Where is My Cad

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BigD

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Joined: Mon, Nov 26, 2007
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Got it!  Assign a visibility parameter to each of the 4 lines.  Then create a formula for each of the visibility parameters.  See the attachment for the formulas.  Works like a charm based on the Extension Dimension.

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BigD

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Joined: Mon, Nov 26, 2007
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I used "Start" and "End" in my parameter names rather than "Left" & "Right" so as to better coincide with the Out of the box parameters.

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seniorcad143

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Can I ask what are the boxes with the check marks under value - what do they represent?

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Yeesh - Where is My Cad

Yeesh - Where is My Cad

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BigD

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Joined: Mon, Nov 26, 2007
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Yea, those boxes are based on the value of the Start Extension and the End Extension.  In the example that I uploaded, both of those are set to 2'-0", which is of course greater than 0, so the forumla causes the boxes to be checked.

If the forumla is TRUE, then it checks the box (makes visible).  If the formula is FALSE, then it unchecks the box.

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seniorcad143

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Joined: Fri, Oct 2, 2009
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It keeps telling me if I put one symbolic line over another that they might loop - did you get that warning?

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Yeesh - Where is My Cad

Yeesh - Where is My Cad

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seniorcad143

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Joined: Fri, Oct 2, 2009
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I also thought that maybe I could just use two lines, one on each side of the center of the joist and just use them for the visibilty, then it would turn off if no extension and the joist would be the way it was out of the box.  It worked on one end but not the other.

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Yeesh - Where is My Cad

Yeesh - Where is My Cad

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