Native extrude and GSP extrude

The difference is no split at tangents. It’s important to have splits at tangents to export clean geometry to other applications.

Rhino made an extrusion and Grasshopper a polysurface. I think Extrusion object is not used by Grasshopper.
You can use Rhinocommon to make Extrusion in Grasshopper.

Yeah I realize that. This was workaround. Thanks. I wonder if tangent will split for sweeps too or not.

Same problem with sweep though.

I am not in McNeel, but why is it a problem ? If I remember well extrusion were new in V5 and they were made in order to be “light” in size.
See this it could be useful

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I understand the difference between Closed Polysurface/brep and extrusion. I’m only concerned about vertex information of curve which is to be extruded. It is not transferred to extrusion as it was done in native Rhino command. See the image again. For sweep, the split tangent problem is both in Rhino command and Grasshopper.

Would be much easier to see if you had posted code instead of only an image. That was my first question; by examining the curve you are extruding, I could answer it for myself.

Yes, the code is straight forward as you can see in image itself, I guess it is self explanatory.

Information is there, extrusion deconstructs the curve because it is a polycurve, extrusion needs “pure” curve .
Left Rhino, Right Grasshopper

The best for you is to ask @DavidRutten if it will be possible that Grasshopper output Extrusion or Polysurface with the same logic as Rhino and for what reasons (export, size of file …). A right click option seems to be good.

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The simple code isn’t the point, it’s the specific curve you are using, how it was made? Details! Whatever.

@laurent_delrieu has just demonstrated the point I was trying to make (thank you Laurent!). The nature of the curve being extruded can’t be determined from a screen shot. Posting the code/geometry answers that question? Why is that so hard?

When trying to help people here starts feeling like pulling teeth, it just isn’t fun anymore.

Yes, you have demonstrated my concern, that’s exactly what I was pointing out. They seemed to work differently. Split tangents, (left one in your image) is more suitable situation for export indeed.

The curve is simple closed polyline with three fillets. The tangent split doesn’t seem to work in grasshopper as Laurent also demonstrated.

why not extruding/sweeping it with already exploded curves? you can also split a curve/surface by analysing the knotvector(-list) and split at them, making it a rational bezier spline…

Grasshopper is working well, for sure. It uses Rhinocommon, the only difference is Davis had to make choices that are not the sames as Rhino developper. They both use the same library but Grasshopper has for example no click from the user so offset has to decide which direction to go, in Rhino YOU chose. For the extrusion it is surely more consistant to output Brep/polysurface. There surely will be an harmonization in GH2 and Rhino xxx.

Because the exploded profile curve doesn’t hold up the profile if they are exploded and then sweeped. Talking about option you suggested for extrusion, I have other simple workaround as you can see in image.

Your point is not valid since if I explode rhino extrusion and grasshopper extrusion, it will not make same amount of individual surfaces. What if I want to explode extrusion in grasshopper and use surfaces to work?

no that is not true, you can always getting it from isocurves back. if extruded, surface parametrisation is always directed the same way. where is it exported at?

Take a look at this example. exploded profile curve does not maintain profile after exploding to segments and then sweeping. And while joined, they do not split at tangents. Both in extrude and sweep. I hope you understood what I mean now.