From the course: NX: Class A Surfacing

What are splines? - Siemens NX Tutorial

From the course: NX: Class A Surfacing

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What are splines?

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- [Instructor] In NX, we have a tool called Studio Spline. Within Studio Spline, under the Curve tab, we have a couple of ways that we can create splines. We have Through Points and By Poles. With the Through Points option, I'm going to come in, specify the plane that I want to draw on. This case, it's going to be the XY plane. And once I've done that, I can begin dropping points out in space where I want those through points to go. Now, you'll notice that I get these hard corners through those points on that spline, and the reason is, is because I have a Degree set to 1. With this, if I increase that Degree, I'm increasing the amount of math per each one of those segments. And with that, I'm able to get a smoother spline running through those points. If I come in now, select this down arrow, and say By Poles, you'll notice I get a little message that pops up, and it's telling me that the spline cannot be constrained in the prior manner that it was. The math has changed. I have six poles, it's a three-degree, so I know it's a multiple segment spline. So, what I'm going to do is I'm going to turn on Single Segment, and you can see that, as soon as I go into Single Segment with those six poles, it radically changes the shape of that spline. The reason behind it is, is because forcing a spline that once had multiple segments, those invisible segments across knot points, to now be removed and form a single spline. And with that, this is the simplest, smoothest possible condition for this spline. If I reduce the Degree, I'm going to remove some of those control points, and now I have a third-degree or a fourth-order spline. You can see I can move those control points around. I can go down to a second-degree or a third-order spline. Move that control up around. And again, it's constrained to that plane. And here, if I begin to increase, you'll notice that it adds those control points. If I right-mouse-click on a control point, I can also add the degree here. I can insert a pole, Previous or Next. So, if I go Previous, you'll see it puts it in between the prior pole and itself. And once again, I have that kind of control more localized because I have a lot more of those control points to that area. And again, it's constrained to that plane, so I don't have to worry of it coming off of that plane. Going to select OK. If I rotate the part a little bit and I go back into Studio Spline, specify the plane that I want to draw on, and this time, I'll just start out with By Poles, leave Single Segment turned on and drawing away, you'll notice that I don't get those little hard points, those corners. It knows it's a single segment. It knows, based off of how many control points I've created or picked, that it's going to be, in this case, a third-degree. If I select another control point, you'll see that it ups that Degree. So, there's a lot of things going on automatically within the tool based off of your selections. So, if you want a third-degree curve, you have to either change this to be a multi-segment spline, which adds a lot of complexity, or remove one of those control points to take it back down to that third-degree. So, it's one of those things. You're going to have to find a balance as you're working through that spline operator.

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