Flow Along Surface closed polysurface

I want to flow my closed polysurface on a surface. But te result is always an open polysurface. Does anybody knows what I can do?
Thanks!!Balustrade.3dm (15.0 MB)

Hi Mathilde - the result is closed here… Balustrade_PG.3dm (8.2 MB)

Works for me with result a closed surface.

Object to be flowed - balustrade, careful to not also select the blue surface
Base surface - green surface, selected lower left corner
Target surface - blue surface, selected lower left corner

thank you!!

But… what are you doing differently to get an open object? Is that repeatable?


I did the same as David said but the polysurface was open… So don’t really know what I did wrong.

How did you determine the polysurface was open?