Hi John, a NURBS surface is fundamentally a 4-sided thing, to make one in the shape of a triangle means that one of the surface edges will be squished down to a point and that will tend to leave the kind of artifact that you show when the point is not a natural type of "pole" of the surface as it is with something like a cone or sphere.

So to get a better quality result you would need to use a 4-sided curve layout for the Network and then trim it, or maybe divide it into 3 separate sections. Trimming a sphere like Stefan shows is a good method.

- Michael