Thursday, 11 June 2015

Hollow Section Sweep with Adaptive Profiles in Revit

Two years ago I posted a description on how to use adaptive component profiles to create a swept blend form in the Conceptual Massing Environment (CME).  Recently someone asked how to create a hollow steel section sweep in CME.  I realised that I had neglected to mention something about adaptive component profiles that makes them different in yet another way from the traditional family editor:

Traditional Family Editor vs Conceptual Massing Environment - (again)

When you create a profile family in the traditional family editor it is by nature a 2D element (this is dictated by choosing the profile template to create the family).  It also has rules about what it should contain - basically it must be a single closed loop (or chain) of lines/arcs.  When you try to assign it to another family, Revit will pretty soon tell you what is wrong with it if you don't follow the rules:
 In the CME, you have to just create an adaptive component that has some lines in it.  Only you (and your naming convention) know that it will be used as a profile for sweeping or lofting forms.  If you try to create a form using an adaptive profile that has a loop inside a loop, Revit will tell you that it does not like it at all - but absolutely no explanation why:
Select a path and two profiles with nested loops
Extremely unhelpful error message when you try to create a form

How to create a hollow section sweep in the CME

The first step is to create an adaptive component profile that only has a single chain of lines/arcs - this is by nature a flat 3D family.
  • Then the profile can be loaded into another adaptive or mass family (external or in-place) 
  • Host the adaptive profile on the sweep (preferably using points to get maximum control).  Refer to the post on swept blends for more detail.
  • In this example I have only hosted one profile at each end of the sweep, and they are the same size, but you could have different sizes and intermediate profiles to create a lofted form.
  •  Select the path and two profiles
  • Create Form - it should create a solid sweep form providing the path is not too tortuous for Revit to handle.
  • Place two more profiles (smaller this time), preferably hosted on the same points
  • Select the same path plus the two smaller profiles
  •   This time create a void (use the drop down arrow on the Create Form icon)
  • Revit should then carve out the inside of the sweep to create a hollow form
If it does not do so automatically, you may need to use the 'Cut' command to cut the void from the solid form. 

Voila - a hollow steel section sweep.  Both the solid and void forms are hosted on the same sweep path so they will move when it changes.

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