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In this video, we continue to explore the use of Rhino's preprogrammed 2D shapes, but focus on the curvy ones, which includes arcs, circles and ellipses. The generation of these shapes is, again, fully automated, but the difference from the polygons is you would rarely want to build these manually, and they do not explode into individual segments. It's worth noting that in this section, there are options for every possible variation, but they're probably only a few that will make sense to you. I'm going to start off by opening several toolbars here, so I'm going to use the commands for a bit. So again, we click on the icon and then next click on the title bar there and drag, so it just stay open. And open up the Circle, click, drag and move and the Ellipse. Zoom in here.
Start off the basic Arc, which is just from your Center. Define a start point. I'm just going to eyeball this here. I am going to hold down the Shift key to constrain it to 90 degrees, and then rotate around to look at any angle or again, type it in at any time, 65 degrees. Next Arc will be this Tangent to several Curves, very handy. So we're going to just pick the curve, and it's anywhere at first, and I pick the second curve anywhere, and then we can pick the points where it's intersecting and notice that there are several solutions. It can jump around inside and out, or even flip the other way.
So, I'm just going to move up here. It's asking for a Third curve we can snap to. We don't have to do that and we can also type in a radius at this point as well. So, you have to go over to the Command line. Click Radius. I'm going to just type 15. Arcs also give you several solutions here. It could go both ways, so right now it's just waiting for me to click on one side or the other. so this is the tool you'll probably use the vast majority of the time.
One more variation is this three-point Arc here, so we're going to just start off by clicking on two End points and then without even worrying about the Radius, you just pick somewhere along that curve for its maximum variation from the other two, or you could type in radius. That is always available. Let's take a look at some of the Circles. I'm going to zoom over here. The most common Circle creation method is with the Center, Radius, just snap that intersection, just eyeball the first one, pretty straightforward.
Now let's get a little tricky. I'm going to create a circle that's Tangent to 3 existing curves. So, we'll pick anywhere along these three. By the time you pick the third one, there is only one solution. So, that's Tangent to 3 curves, one is a circle, two are arcs. Let's try with some straight lines - same commands. I'm going to right-click, pick these guys anywhere and again, there's only one solution. And here is kind of a specialized circle creation method, but it's pretty cool, the way it works.
This is called Fitting Points, so you have to have points in the scene. Now if I want to snap to this End point, I'm going to have to go ahead and create a point there, so that's pretty straightforward to do. I am going to go over to the main toolbar here, select that Point entity and just snap one there to End the line. It's that easy. So, I'm going ahead and start this command one more time. Fit the points, just select those group and when I'm done, I hit Right-click or Enter, so it's taken the common center, that's the center of the circle, and then average the distances away.
Let's check one more way to create some circles around other curves. We just did this recently with the Polygon command. However, with Circles, you will probably be doing these far more often than Polygons. For this, I'm just going to stay with the standard Circle command, which is the one you'll see here on the main toolbar, and it's not just buried and customized as the other guys. I'm going to explore some of these options though, so we've got what looks like 5 or 6 different ways to create it. I'm going to select AroundCurve, select this straight segment, and we'll just snap to that point. We can draw out.
I am just going to click randomly for radius. And so that's pretty nice. It figures out the exact perpendicular angle, which actually is pretty easy for a straight line. Let's try it on that curved segment, Right-click to repeat. Circle command, select the AroundCurve option and select this arc over here and start anywhere. Notice my cursor tooltip is giving me dynamic feedback, so you can kind of eyeball and get close. But if for some reason you have to match another dimension elsewhere in the file, you could type I need 5.5, typing that in the Command line in top, Enter.
So, that's a specific diameter. We'll do one more Circle. We're going to select the Tangent to 3 curves that show how you can use it with only 2 and get some extra options, so I'm going to select this arc here, this curve line there. Now it's asking for a Third curve somewhere else. Instead, I'm just going to hit Enter to use the first two, so let's undo that with Ctrl+Z and try it one more time. I'm going to select the Circle, Tangent to 3 curves, pick the first one, second one, and you can dynamically move around or this time, I'm going to type in an exact radii.
You have to check the radius option, type in the new number, and there's the solution. So, you're using the Fit to 3 curves but only having two, and then you type in a radius. Let's check out some Ellipses. I'm going to zoom over. I'm going to start off with the most basic ellipse command, which is from the center, and then to edges. Start off with the center, one of the axes and then define the second axis. That's the most common.
A lot of times, you will probably have a opening where you need to fit a shape like an ellipse into, so we can define it by the corners. So, we just snap it the opposite corners and then, finally, may have an area available where you know just one of the diameters, not the other, so you can select those. You can snap to it. I'm going to hold down the Shift key, so I constraint that to 90 degrees and I just select anywhere or, again, type in an exact value. At this point, it's worth mentioning that there is a common mistake that will happen many, many times as you learn the software, and that's when you've unexpected results.
It just means you probably forgot to read the options available on the Command line, so do a quick undo with Ctrl+Z and start the command over. This technique is very simple and may include just going a little bit slower and reading it another time. It sounds easy but will serve you extremely well in most situations.
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