Rhino 6: Extrusions explode to single surfaces. Is it a setting?


sorry, me again. I wonder, extrusions explode to single surfaces in Rhino 6.

Is this a setting? I would expect polysurfaces.



Hi Michael - I guess it depends on the extrusion - can you post one that you’d expect to be ‘poly’?



Hi Pascal,

sure, here a video and the file: Rhino_6_Extrusions.3dm (31.4 KB)




Hi Micahel - ok, I understand what you mean - I thought you meant exploding to multiple faces or single faces (According to tangency) Yes, that is true - same as V5, actually.


If you want a single extrusion to become a single polysurface, you can use the ConvertExtrusion command.

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Hi Wim,

thank you very much, and I know ConvertExtrusion. I would like/expect that explode first converts an extrusion->polysurface, and polysurfaces->single surfaces.

That’s much easier, faster, and more logical to me, than searching and thinking about ConvertExtrusion.



Well, I would not like to have to explode an extrusion twice to get at the underlying surfaces… Especially if you don’t really know whether the object is an extrusion or not…

In the general case, I recommend against using extrusions as a default setting, they have no real practical value IMO for the average user, and the advanced user that does need them will know to turn them on. But I have never won that argument…


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Not necessarily unreasonable - but the thing with extrusions is that they are designed to convert into NURBS on-the-fly so that the user doesn’t have to think about them as being special objects. If you would have to convert them to polysurfaces each time you want to perform any operation on them, it would definitely become a drag to use them.

Completely agree with you there…

100% with you on this one. I think they should be ‘off’ by default. I have seen a lot of cases when non-advanced users are confused by the extrusion objects and the way they behave and having no idea of real advantages of what they were designed for.

I also agee. This is part of the promotional material about extrusion objects when they were introduced in V5.
Lightweight Extrusion Objects [McNeel Wiki] How many users today will have models with a large enough number of simple shapes which can be represented as extrusions that they will see a noticeable improvement in performance using extrusions? My guess is the answer is probably different than it was ten years ago or more when development of extrusion objects started.