Extrusions in Dynamo

[ksobon]

This is more of a wish than anything else. When creating an extrusion in Dynamo the output is a single surface object. On surface (no pun intended) that seems to be correct but a lack of methods available in Surface class makes this a very difficult object to work with. I am not sure what the correct solution can be implemented but something like an Extrusion class would be nice. Ability to query base curve, distance etc would be desired in this case. I haven't looked at Lofts and Sweeps, but I also haven't seen any classes for those so I am guessing that they are either PolySurfaces or Surfaces so very similar issues will arise.
Another, thing that makes working with Extrusions difficult is method PerimeterCurves() that returns a flat list of curves. That list includes a seam curve. Given that they dont have any properties that would identify them as seam curves it makes it very difficult to filter those curves out. Also, in case where a multi-segment surve was used to create the extrusion that list of perimeter curves will have all of them as individual curves where a much better solution would be to return a single polycurve object.
These are just some of the thoughts that I have based on few minutes that I spent looking at Extrusion objects. All comments are welcome:
@HLP @kronz @pboyer @holyjewsus

[kronz]

Hi Konrad,
Interesting. Yes, I can see your concern here. The seams you are identifying seem (no pun intended) to indicate an internal confusion. The "surface" extrusion is funny, in that it acts like a single surface bent around on itself (with 2 coincident "internal" edges), can be exploded out to many surfaces, and just straight up fails on Surface.Closed. It's entirely sensible with a closed curve, like a circle or ellipse, and I think you can do everything you are asking to do with a the polycurve result if you convert the surface to a polysurface.

I don't think we should solve this confusion by adding an Extrusion class, as the whole geometry library is set up around the idea of the result (solid, surface, curve, etc) rather than the action that creates it (loft, revolve, etc). Perhaps we need more tools for querying Surfaces?

[ksobon]

@kronz yes, so exploding and converting it to PolySurface seems like a possible workaround here, yet my concern that in case of a Polygon or PolyCurve extrusion the output should be a PolySurface by default. That would solve the issue of UnconnectedBoundaries() not being available for Surface class but being there for PolySurfaces. I still stand by my comments about identifying edge type by giving output curves an appropriate property. Who knows maybe i will need to extract seam curves and not always just naked edges...