What's the difference between Surface vs Open Polysurface

I would like to know what the differenece between an open polysurface and a regular surface is. is there any advantage or disadvantage between them.

In the photo the surface in blue is the open polysurface and the purple one is just a regular surface. Both surfaces were made from curves using the EdgeSrf command, why does it sometimes generate two different surface types.


Hello - a polysurface is two or more surfaces joined at the edges. If there are no unjoined edges, then the thing is a closed polysurface.
EdgeSrf, like Loft, pays attention to the structure of the input curves - if these have kinks, or hard corners or fullt multiple knots then the output is likely to be split into multiple faces (a polysurface) at those locations.


Hi Pascal,
Thanks for the explanation! However, is there a quicker way to “close” the open polysurface without rebuilding the input curves? if the model is built for quick massing purpose.


Planar openings on open polysurfaces can be slosed with the _Cap command