Rebuild Crv creating duplicate points - SOLVED, sorta


OK - perhaps a premature post - MakeUniform allows for caps - however, I don’t understand the duplicate points. They also exist in the curves made uniform.

Original post:

I’m having trouble extruding (tapered) capped surfaces from some curves. The curves are from dupedge, rebuilt, remapped to cplane, and rebuilt again. The reason for all the steps is that there are numerous curves I’m dealing with. Non symmetrical geometry.

Thing is - I rebuild one of the curves with a pt count of 21. Upon inspection, however, there are 5 duplicated points.

Any explanations?



This is normal, a closed periodic curve will report degree number of “duplicate points”.



I suppose I ought to be thankful for you not delving into the mathematics of it! I can accept ‘normal’.


(Menno Deij - van Rijswijk) #4

A periodic curve is basically a curve that has the first d and last d control points (where d is the degree of the curve) the same, together with a non-clamped knot vector. In Rhino though, you see the duplicate control points as single control points, which makes it easier for the user to manipulate periodic curves.

This in contrast to closed and open curves, that have a clamped knot vector. This means that the first and last control point are also the start and end of the curve, respectively. A closed curve has only a two overlapping control points (first and last).


Ok - so the 5 duplicates is purely based on the degree of the curve. Or in this case, 5, yes?

Thanks for the explanation menno.


(Menno Deij - van Rijswijk) #6

Yes: #duplicates = degree