Why are these extrusions displaying differently? They were both extruded from the same curve. One was a straight extrusion, the other an extrusion along a curve. I have shown the object details and they are different in the number of faces. Why, and how can I make them view the same in the shaded view?
Rhino is set by default to make internal G1 (tangent) joints as one single surface when extruding (very bad idea, but still haven’t gotten that behavior changed after years of complaining). Both of the extrusion methods you used have an option to change this default behavior by setting the SplitAtTangents command option to Yes. I suspect that your straight extrusion has had this done, but your along curve extrusion - which is a separate command - does not…
You can fix this on the existing objects by unselecting them first, call DivideAlongCreases, set the option SplitAtTangents to Yes, then select the straight extrusion. That should make the two look the same and they should both then be polysurfaces with 12 faces.
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Thank you. I learn something new every day. 
Me too… 