BILT Speaker

BILT Speaker
RevitCat - Revit Consultant

Monday 20 July 2015

Tightly Curved Swept Blends in Revit Adaptive/Massing Environment

Following on from my last post about 'Unable to Create Form Element' in the Revit Adaptive / Conceptual Massing Environment, here are a few ideas about how you might just solve the problem.

In the conventional family editor, Revit does not have any major problems in creating swept blends along a single path (one spline or arc or line), unless the radius of a curve on the sweep is too small and causes impossible geometry.  For example this simple sweep of a profile along a spline takes a minute or two to create:

In the Adaptive/Conceptual Massing Environment (CME) you have the added ability to loft shapes - to create blends of more than two shapes/profiles.  However, the rules for getting them to work are immensely more complicated, and often quite baffling.  Below is a particular workflow that I was using just to test a process, and it caused all kinds of issues.  Hopefully it might give you some clues as to how to solve similar problems - particularly if the path is more complex.

Creating Swept blends / Lofted Forms along a tightly curved path in CME

  • Place three points 
  • Select the points
  • Create a spline through the points
  • Adjust the spline to have a fairly sharp transition by dragging the middle point
  • Host some new points on spline
  • Host some adaptive profile components on the points
  • Select just the profiles
Select Profiles
  •  Create Form - it fails
  • Try pushing points closer together

  •  Select profiles; then create form - it might work if you are lucky
  •  Maybe you can pull the points back along the curve
  • At some point you get the 'No Entry' sign (circle with line through it), meaning it will not allow you to push the point that far along the spline
  • Try picking the control point for the spline and make it less of a tight curve
  •  Then maybe you can extend form by pushing the points out
  • If it is still not creating the form, you may need the spline to be really gentle to start with before you extend the points out to the ends of the spline
  • Point locations along the spline can be controlled by properties, or you can even make it parametric - using the 'Normalised Curve Parameter'.

  • Intermediate points may also need to move to get a better spread along spline
  •  Then try pulling the spline back to a tighter shape - Revit will most likely allow you to create a much tighter shape than it would originally
  • At some stage you'll notice that the form does not follow the spline, it just creates its own shape by linking the profiles
This may or may not be what you want.
  • If you do want it to follow the spline exactly, your life will be easier:
  • Dissolve the form
  • Select the profiles and the spline
  • Create Form again, and Revit will be much more forgiving - it is more likely to create the form with a tighter curve or one that turns more than 180 degrees on itself.  The obvious difference here is that it knows which order to link the profiles.
  • It uses the spline as a path but only extends between the first and last profiles
If you adjust the spline further, until the shape is too tight it will eventually tell you that it cannot create the form.  I have not figured out yet what the rules are.

What I have figured out is that if you go away for a while and drink a delicious cup of coffee brewed by your local barista (preferably a cappuccino), and come back to try again, you will usually have much more success with pulling the spline around into tighter curves with ends that even extend past each other (but not crossing).

Honestly, it is true that if you are too ambitious with the shapes initially Revit cannot cope.  But try adjusting them later and it works much better.  So the moral of the tale is that Revit gets a boost from caffeine just as much as you do.
More thoughts on lofting and swept blends to follow . . . .
Part 1 - Creating Sinuous Curve Swept Blends in Revit Adaptive/Massing Environment
Part 2 - Creating Revit Swept Blends along sinuous multi-segment paths


  1. Have you noticed whether it fails to create these lofts at specific intervals during the month? :)

  2. Hopefully you can teach us also how to use python in revit...more power.