In this video, we'll take a 3D tour of the fundamental entities that comprise the Rhino universe. There are technically four Entities, but the Point Entity doesn't really count, since it's used mostly as a reference, or a marker, and not at all for modeling. That leaves us with three, the Curve, the Surface and the Solid. It's easy to keep these clear if you just look at the menu and see them organized one after the other, Curve menu, Surface and Solid. Let's start the tour. I'm going to zoom in. Here's our basic Point Entity.
You can find that on the main toolbar right here, first position. Here's a couple of different kind of Curves. Even though some are straight and some are free form, these all are technically defined as Curves. We have open variety and closed. One fundamental aspect of Curves is you can turn the Control Points on, so I'll just light those up. I'm using the F10 shortcut. It's important to know. We'll discuss later. Next up is Surfaces, so we have just the flat plane here that would qualify as a Surface, and this more organic shape qualifies as a Surface as well.
Doesn't matter the shape. We have two kinds. Surfaces can be trimmed with holes punched out. There is the flat plane, and here is the more of a Freeform shape. And any of these can also have control point curves turned on as well, so I'm going to go ahead and do that, using the shortcut key, F10. This just means with the Control Points' ability to turn on, they're still editable. We can move things around. That's in direct contrast to a Solid, which is no longer editable, at least with the Control Points.
So, we here have a couple of basic primitives. This is a cylinder, and that's a cube, pretty obvious. Those are considered closed Solids. That's important too, because once an object is closed you can then make a prototype from it. It's interesting that some open Solids still are considered technically a Solid, because you can do some commands on them. For example, we have this shape here, and it's got one face opening. This is a good opportunity to discuss the relationship between Curves, Surfaces and Solids.
You can build one from the other but also extract, or go backwards to the prior Entity shape, and in this case, we have an almost fully closed Solid. I'm going to go ahead and just do a quick cap on that top, cap the planar holes, select the object, right-click. So, now it is converted from a Solid that was open to a Solid that is closed. Okay, now here's another pretty open Solid. It's got a couple of faces missing, and just as a quick example, we'll use some commands that are specifically designed for Solids, but they work on this object, even though it is just a group of surfaces joined together.
So, let's do a quick demo out of Fillet, select that edge there, and just do one more Fillet the other direction, type in a smaller number, select these edges in sequence, right-click to accept. So, there is a Solid Fillet command that's been actually performed on a Solid that was not fully closed. And then we have this Single surface that forms a Solid, because it's been wrapped and closed.
So, here is an example of one of those, a Sphere and the Torus. So, there's only one surface there, but there is no openings, so it's kind of the rare animal that is a Single surface but also a Solid at the same time. Let's take a look at the Multiple part Entities. So, anytime a Curve is joined to another Curve, whether straight or arced or Freeform, those are called Poly-curves. So, here's a couple of straight-edged examples. Here's a combination with an arc, here's a combination with a Freeform Curve and a couple of straight-edged.
Now remember, you can always go forward or backward, so we could use these to create a Surface, or break them apart and work on the individual segments and then rejoin them. Next up is the Poly-surface, pretty simple definition. We just have more than one Surface joined and has to be at the edge. So, if they overlap any other way, it will not be possible to join them together. Okay, here's another example with the Freeform Curve, which has been extruded to a Freeform Surface, and then to flat planes, all joined together as long as they share a common edge.
And another more involved example with the Freeform Curve, some straight sections, we have some openings that have been trimmed out. One final note on the Poly-surfaces: after a Multiple Surface has been joined you cannot turn on those Control Points. So, if I were to select any one of these and hit the F10 shortcut or the turn Control Points on, it's not allowed.
You can see here at the command line. We cannot turn them on. Not a problem, still you could detach those from each other, and then turn the individual Surface Control Points on if needed. So, those are the Entities that can be set to be the foundation of all the Rhino modeling. This 3D tour is critical to the understanding of how all Entities are closely related to each other, and by related, I mean you can quickly draw a Curve and then extrude it into a Surface, and then when Multiple Surfaces are completed and have no openings, they can then be joined into a solid. Conversely, you can also go backwards at any time and explode a Curve into individual segments, or explode a Solid into individual Surfaces.
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