From the course: Learning Rhino 6 for Mac

Solids basics - Rhino Tutorial

From the course: Learning Rhino 6 for Mac

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Solids basics

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- [Narrator] Some surfaces in Rhino for Mac, fall into a special subgroup called solid objects. I've got some examples of them here, in the exercise file, solids-basics.3dm. Unlike in real life, solid objects and Rhino don't actually have anything filling the interior. They're still made of the same infinitely thin mathematical surfaces as non-solid objects. In Rhino, a solid is made anytime a surface or a polysurface is completely closed. So that is, when all of its edges meet up exactly with other surface edges, with no gaps in-between. And there are basically three types of surfaces that can make a solid object in Rhino. First we have single surface solids, like these two. So we have the sphere and the torus. Those are both examples of single surface solids, where the surface is stretched, so that every edge matches up to another edge exactly. We also have polysurface solids, so we've got the 20-sided icosahedron and the cone. Those are both examples of multiple surfaces that have been joined together into solids. And last but not least, we have extrusion solids like these three. So the box, the cylinder and the freeform extrusion, these are all examples of Rhino's lightweight extrusions. And even though some of them have multiple sides like the box, they're not technically polysurfaces. These are shapes that are defined simply by a profile and a height. And they're defined this way, just to conserve memory in Rhino, but they're still technically solid. So how can you know for sure, all these information about any given object, whether or not it's solid, how many surfaces it might have, what kind of solid it is? After all, even a tiny gap between edges is enough to make the difference between a surface being solid and being open. And we can't always tell just by looking. So one of the first places we can check, when we're trying to get more information about whether an object is solid or not, is the properties inspector panel. So that's in the right hand sidebar. So let's look at some of the details of one of these objects. So let's start with the icosahedron here. And in the right hand sidebar, I'm in the properties inspector down at the bottom, I want to click the details button. And this is going to give me some information about this object. And specifically what I'm looking for here is under the geometry section. So I can see this is a valid polysurface, a closed solid polysurface with 20 surfaces. So here it's being very explicit. This is telling me it's a closed surface and exactly how many surfaces it has. Same for the cone here. If I go to the details, valid polysurface closed with two surfaces. And let's take a look at one of these single surface solids. So let's select that tourist there, go to the details in the objects property inspector. So I can see this is a valid surface and a closed surface. And while it doesn't specifically tell me that this is a single surface solid, I can kind of infer that because, it's only talking about one surface, it's not talking about multiple surfaces as it would with a polysurface. Now let's look at one of these extrusion objects. So these can sometimes be the least explicit in terms of the geometry details, but let's pick one, go to the details. So I can see this is a valid extrusion, it's an extrusion surface. So it won't actually be made explicit to you that this is a closed surface, but if we do a little bit more digging, we can look and see what the profile curves are made of. So I can see I have one NURBS circle and another NURBS circle. So that's making the inner and outer edges here of that extrusion. So as long as the profile curves are closed, which by definition the circle is closed and the object has caps on it, then by definition, it is also closed. Let's go over to our layers panel and I'm going to turn on this non-solids layer. So this gives us a few more examples of surfaces that we can look at and I'll just rotate around, so we can see this a little bit more clearly. Now, obviously a surface like a plane is not solid, it has four open edges. If we look at something like the swept freeform surface, we can see, we get a little bit closer to solid. This is closed in one direction, so it does meet up going this direction. But I can see obviously, there's these big open gaps on the ends so that's not solid. This sort of a vessel shape, looks pretty solid to me, as far as I can tell. But of course, the only way we can know for sure is by looking at its properties. So in the properties inspector, let's click on the details and I can see this is a valid polysurface, but it's an open polysurface. So this is not closed. So somewhere in there must be some little gaps that are preventing the surface from being completely closed off. Now, in another video, we'll take a look at Rhino's edge analysis tools, which could help us pinpoint the open edges on this object and fix them. But the key takeaway for now, is that you can't always tell an object is solid just by looking. So be sure to pull up the details.

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