Divided surface bug

One of the reasons that Rhino remains so popular amongst designers is Revit’s primitive conceptual modelling tools. Below is a clear example of Revit’s limitations when it comes to conceptual modelling and how Rhino can help. Special thanks to David Baldacchino from do-u-revit for contributing to this solution.

 A known ‘bug’ within Revit is how planar trapezoidal surfaces are divided. Revit takes the liberty of ‘optimising’ the divisions by treating the surface as a trimmed surface and cropping the UV divisions. There is no way to prevent Revit from doing this, even if you are in Dynamo. This can causes major problems, as often one needs the UV divisions to follow the surface, not some imaginary trimmed surface.

In order to make the trapezoidal surface with a skewed UV grid, there are a few workaround options. Unfortunately, none of them are great. The first workaround is to displace one of the vertices a very small amount, say 1mm, so that the surface is not a pure plane. Clearly this is not ideal and very inaccurate.

The second workaround is to set the number of  ‘V’ divisions to zero and use intersects instead. To do this:

  • Take the top and bottom edges and divide the path.
  • Set the number of points you want. This will be the V grid divisions.
  • Add reference lines between these nodes. Note: these cannot be used as intersects as they are not plane-based.
  • Create reference planes by picking these reference lines and use them as intersects.

Neither workaround is great but until Autodesk decide to fix the problem, and it is a problem, this is the best we can do.

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