> In R4, a 2-rail sweep will produce the frame as a single creased surface (point editable).

Hi Jonah, I couldn't seem to replicate this - is there a special setting you used to enable a single-creased-surface result in Rhino?

Over here when I do this type of 2-rail sweep in Rhino, it generates a polysurface split along the kinks, and trying to turn on control points results in a message: Cannot turn on points for polysurfaces.

One thing you might be interested in - the result of this 2 rail sweep in MoI remains point editable despite it being a polysurface. This is because MoI supports a feature where you can edit the control points of a polysurface if the joined edges of the polysurface are natural surface edges and have the same control point structure along the joined edge. This is convenient because the output of surfacing commands with kinked input curves generate such structures. Also for example a simple box is point editable in MoI.

- Michael