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# a question on how to set the first and end point as interpolation points for NURBS in NX

Pioneer

Hello, everyone,

Now, I am able to use  "extract geometry" in NX to convert a cylinder face into a B-surface and get nodes(poles) of the B-surface. But in order to output the closed surface and show in Rhino, I need to set the first and end nodes(poles) to be the intepolation points for closed surface.

As shown in the left graph, it's a circle drawn in Rhino, the first and end nodes(poles) pass through the curve. (intepolation)

But in Nx, the first and end nodes(poles) doesn't seem to be the intepolation points.

My question is that how can I manunipate the nodes(poles) of NURBS in NX in order to convert them from control points into intepolation point?

2 REPLIES

# Re: a question on how to set the first and end point as interpolation points for NURBS in NX

Legend

Maybe if I explain what you have for the two cases.

The circle in Rhino is a rational B-Spline consisting of 4 degree 2 segments.  This gives you 4 poles on the curve and 4 corner poles which have a weight of cos(45).  The 4 poles on the curve are also knot points.

The cylinder end edge is also equivalent to a rational B-Spline but it consists of 2 degree 3 segments.  This gives you 2 poles on the cylinder edge which are the two knot points.  The 4 corner points have a weight of 0.33333.  The rectangangle is 2xdia by dia.

Frank Swinkels

# Re: a question on how to set the first and end point as interpolation points for NURBS in NX

Siemens Phenom

When Rhino itself constructs a circular b-spline curve, it looks like it uses 4 segments of degree 2, as Frank described. What you're seeing as the edge of a cylinder in NX is a b-spline curve that has two segments of degree 3. You should be able to transfer the NX curves and surfaces into Rhino, even though Rhino would not create these sorts of geometry itself.

Why don't you just use IGES ??