Wednesday, July 24, 2013


Lots of people to credit here, but I'll point the finger at my good friend David Light and this recent post.      EMPIRE BIM

Each to his own, and as it happens I'm not particularly addicted to Star Wars. Maybe it's a generational thing.  But if you've followed this blog for any length of time, you'll know that I do have a thing for Musharabiya screens.

Make a new family, starting from a "Planting" template.  Go to the front elevation, use reference planes to mark out a square.  Mine is 1m x 1m. Make an extrusion within this square.  I started with something pretty boring, impatient to see results.  Nest this into another planting family & position at the origin (centre).

Nest the host planting family into a curtain panel family.  Again place at the centre.  Place a height dimension and make it a reporting parameter.  Mine reported 4m.  In type properties, set the height of the planting family to match this measurement.  It will scale, as all good double-nested planting families do.

Load into a project and make a curtain wall type with square panels and no mullions.  You need to size the wall so that there are no part panels at the edges.  I used an 800x800 panel and made the wall exactly 4 modules high by 7 modules long.

Set the panel type for this CW family to the panel family you have just made. Bingo.

Now try halving the module.  Just change the height & width parameters in the curtain wall definition.  All the panels resize like a charm.

Once you get the idea, it is easy to do some recursion.  Select a panel and unpin it.  Use the type selector to replace the panel with a wall type.  Choose a curtain wall with half the module size.  One panel becomes four.  Repeat this procedure to make ever smaller cells.

One of the drawbacks of this kind of blanket scaling is now revealed.  The panels get thinner.  We are back to CAD-style dumb scaling.  The whole idea of parametric modelling was that you had separate control over different aspects of a component.  Change the size of a door without scaling down the door frame or ending up with a non-standard thickness for the door leaf.  In our enthusiasm for clever new tricks we tend to forget these fundamentals.

So what if I wanted all the panels to have the same thickness ?  There is a way, and it's not too hard.  Go back to your original "nested planting" family.  Add a thickness parameter to control the thickness of the extrusion.  Define that thickness as "Height / Thickness Ratio".  Load back into the "host planting" family.

Link the "Thickness Ratio" parameter of "nested planting" to a matching parameter in "host planting".  Load into the curtain panel.  Link parameters again.  Now you can create different types with different "Thickness Ratios"   Basically if you know that the panels is half the size, just halve the thickness factor and the thickness will match the larger panel.

You can achieve subtle variations of thickness now, it is no longer totally dependent on panel height.

I went on to make a few more panels.  This is very easy once you've set everything up.  Just change the name, edit the original extrusion, load back, load back, load back.  Set a curtain wall to use the new panel.

This is the fastest method I have yet found for making a variety of screen designs with a module size that is easily adjusted.

One big drawback though.  You can only have whole panels.  No cutting and shaping at the edges.  Forget it.  Best I can think of is to make all the cut panels separately as Generic Models and place them one by one.  If there are part panels in a horizontal row, Revit will give you baby panels centred, with gaps between, as in the image below.

So it's an interesting technique but time alone will tell whether it will be useful on real projects.  Maybe for early studies where you are experimenting with module sizes.  Then once the module is fixed make families similar to the ones in my second ever post


We are still using these.  Done solid service on several projects.  But changing the module size is a bit of a pain. Not too bad, but can't be done in a matter of seconds like you can with the planting version.  So once again, the best method for early design may not be the best method for construction documents.  No surprise there.  Always been the case.  6B pencil versus 4H.  Work smart, be flexible.


  1. Andy,
    I can't imagine my planting trick has been influencing all you guys to do scaling experiments. Scaling is the hottest topic:)

  2. Hi Kelvin, yes I think it's great to see ideas bouncing around and given different takes by various bloggers. More to come from me on this one.

  3. Hi Andy Milburn ! I sure am gonna be a fun of your blog. Great work !

  4. Hi Andy,
    Great work here. I may have solved your problem with cutting and shaping the edges of panels - by using curtain panel pattern families instead. See my latest RevitCat blog post:

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  7. Hi Mr. Andy,
    i have done the panel according to your esteemed explanation, but i am stuck at thickness ratio linking. could you give 4-5 sentence about how i can do it please?

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