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Your observation is correct. A list of data points to be interpolated (passed through) does not fully determine a spline curve, or even a Bezier curve.
To properly define a spline, you also need to assign parameter values to the data points. You can't do this in interactive NX, but you can in the SNAP API (and in NX/Open, too, I think).
Problems will arise if you have a workflow that assumes that the data points fully define the spline. For example, if you construct a spline curve through given points in two different systems, you should not expect to get the same curve.
I have never seen this as a problem.
Typically one uses the through points method to solve a shape where the points somehow are predefined and must be passed by the spline, the specific shape is maybe less important.
and the by poles method when the shape of the spline is maybe more important than the absolute position of the spline.
I have found that the engineering mind trends toward points, they like to define things precisely. The styilng mind, tends towards poles, for asthetic reasons.
I've worked with both, and use poles to define my splines, as I find they behave better
Hi @Yamada Thank you for your explanation!
I know that there's simple equation for poles: number of poles = number of segments + degrees. I had been thinking about whether there's a similar equation for through points. The situation seems to be more complicated than I imagined.
I try to get some understanding about through points, because a through point is similar to an internal control curve in Studio Surface. A difference is that internal control curves for Studio Surfaces are already assigned parameter values by the boudary curves. I'm just thinking about one qustion: for a degee m×n B-surface, how many internal control curves can be input without causing the surface segmentation.