Friday, October 15, 2010

Parametric Trusses via Curtain Panels

I have long been frustrated by REVIT's inability to divide curves equally.  Its a nifty command in both ACAD and Bentley, but for what ever reason, I can't do this in REVIT yet...with a hopeful emphasis on 'yet'.
So rather than sit around, pout, and send incendiary emails to the program design team, I sought a work around.  The first question is "Why do i want to do this anyways'?

Well, to make an adujsutable truss of course!

After screwing around with Curtain Panels by Pattern for a while, I found a pretty decent work around.  It isn't perfect, but with a little planning, this methodology can go a long way.

First off, I have to make my Panel Pattern.  In this case i have based it upon the rectangle template, but you can certainly do it with triangles as well.

I linked the reference points at the corners with reference lines and extruded solids along the lengths.  Visibility of all the forms is controlled independantly, which will become clearer in a minute.
Next i started a truss form in the conceptual mass editor using a simple rig.  I created reference lines to become the top and bottom of the truss, with circles hosted on reference points at the ends to control the bar diameter.  Then i hit the Create Form button to create a surface between the lines.

Next comes the fun part.  I divide this created surface and turn OFF the U Divisions.  Obviously, I can now change the number of divisions to my hearts content (which is what i wanted in the first place!)
I'll apply the pattern I created earlier and it looks like this, not quite what i am after visually...

Remember that i said the visibility of all forms in the Panel Pattern were controlled individually?  By picking panels individually, I control the bar locations and direction.  I can also eliminate duplicates later on if i want to schedule the elements.

So now i have a parameter driven simple truss.  All the bar sizes can be controlled easily.  Also I can change the number of panel divisions to make it larger or smaller, but when i do that, the bar visibility that i set up goes pear-shaped.  But like I said, with a bit of planning, I can get around this in my project by setting up multiple families and using design options.

You can dowload this example here: