NURBS primitives

- [Instructor] Now, let's take a look at a basic way to create NURBS surfaces, and that's by using primitives. Now, these are very similar to the primitives we use in polygonal modeling, and it's just one way of creating a NURBS surface. We can also create NURBS surfaces starting with basic curves and we'll get to that in just a little bit. So, let's take a look at some of the primitives that we have. So, we can go under the Create menu, and under NURBS Primitives, we have all of these. So let's go ahead and just tear this off by clicking on the double dotted line, and let's take a look at what we have here.

So, the first one is the sphere. And I've got Interactive Creation turned on here, so I can just click and drag. And when we create a sphere, well, it basically creates this shape. Very familiar. But if we go over to the Attribute Editor, we can take a look at some of our creation parameters here. So, if we go into makeNurbSphere, we can change the number of sections as well as the number of spans. And so that just adds or subtracts detail, very similar to how you would see it on a polygonal object.

Now, remember, NURBS surfaces are based out of rectangular patches, so if you want to know how a surface is constructed, look for the seam, and so this double width line here is my seam. And as we've seen before, we can change the sweep of this, either at the start or at the end. So, let's go ahead and select this sphere and delete it. Now, another one is the cylinder. Now, I'm going to skip over the cube for just a second here, and let's take a look at the cylinder.

Now, when we draw a cylinder, it's drawn the same way as a polygonal cylinder, but a NURBS cylinder is actually quite different in that it is comprised of three separate objects. So if I go into Windows, Outliner, we can see this. So, I have this NURBS cylinder here, but notice how this is actually a hierarchy, so if I expand this hierarchy, you'll see that as a child of the main cylinder, we have a bottom and a top cap.

So this is actually separate geometry, so if I select this top cap and move it up, you can see that it's actually a separate patch. Now, the reason we do this is because remember, NURBS surfaces are only rectangular patches, so in order to get this sort of geometry, we have to use multiple surfaces. Now, if I select this cylinder, we can go into the makeNurbCylinder node in our Attribute Editor, and again, we can sweep it and show you how that's created, we can add in spans as well as sections, to add or subtract detail.

Now, if you just want a NURBS cylinder without the top and bottom, you can always select those and delete them, or if you go into the creation parameters of this, so if I go into Cylinder here and click on this little box here, we can actually control some of this. So, I can control the sweep at the start and at the end, and I can turn off caps, so I can either have no caps, bottom, top, or both. So you can control it on creation.

Now, I'm going to go ahead and select my cylinder and delete it. And now, let's take a look at something even a little bit more complex here. So, I'm going to go back into my Create menu here. And let's create a cube. Now, a cube is probably the epitome of stitching patches together because each one of these is a rectangular patch. So, again, if I got into the Outliner here, you'll see that I have a NURBS cube node, and under that are the six sides of this cube.

So, again, each one of these is a separate patch. So, if I select the main node here, and if I select any one of these original nodes here, we can go into our makeNurbCube, and we can add or subtract detail. Now, notice how the detail adds and subtracts for all these individual patches when I dial up one. Now, if I don't want all of these, again, I can just delete what I don't want and create other types of shapes.

And if I want to, I can select the main node and delete it. Now, we have a few more here. Let's go into cone, which is very similar to cylinder. And instead of having two caps, it obviously only has one. So, let's go ahead and delete that. And then we also have the plane, which is very simple, and that's actually just the purest form of a NURBS surface, is actually a NURBS patch. So this is a NURBS patch look like. We can certainly go into our Attribute Editor and dial up our detail.

We can right click over it, go on Control Vertex, and again, shape this. And notice again, how nice and smooth everything is. Right click, go into object mode. Let's delete and let's do one more, and that's the torus. Now, torus is essentially donut shape. And as you can see, this one has actually two seams, so we have a seam here as well as another seam down here. So if we go to our creation parameters in our Attribute Editor, we find makeNurbTorus.

You could see that we have two sweeps. We have a start and end sweep, so this is basically the sweep for this axis. And then we also have what's called a minor sweep. So, as you could see, this again, is a four-sided patch that is just swept into a cylinder, and then that cylinder is swept into a torus. So, hopefully, this gives you a little bit of insight as to how NURBS surfaces are constructed, and these primitives are really great ways to start your NURBS modeling.