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In Rhino 4.0 Essential Training, author Dave Schultze shows how the 3D NURBS-based modeling tools in Rhino 4.0 are used to engineer products from toy robots to full-sized aircraft. This course concentrates on using Rhino 4.0 for industrial design and rapid prototyping, with a review of common 3D terminology using specific examples. Along with a comprehensive exploration of the Rhino interface, the course includes an introduction to building 3D objects with Rhino's three primary entities: the curve, the surface, and the solid. Exercise files are included with the course.
In this video, let's take a look at how to scale objects in one, two, or three dimensions. As usual, Rhino lets you scale just about any object you can select. However, if you stop to think about it, a straight line can only be scaled in 2D because it doesn't yet have a third dimension. Likewise, the point object can't be scaled at all. And when we have a solid or polysurface object, it can then be scaled in any of three dimensions. So, let's take a look at that first situation. Now, a general rule: all scaling is going to require you to select an origin. That's the center where all scaling will be calculated from.
We have just got the latest leg design from the Robot Leg department and we have got a problem. This is way too close to the arm that we created earlier. So, we are going to scale this arm back down. Step one will be to create an origin somewhere on this arm to scale around. I don't have a point located where I might want one. So, let's create one right now. Let me go ahead and turn on Intersection and I am just going to create a one Point object from the menu here and pick this Intersection location.
That's where I want to scale it from. The Scale commands are located here on the main menu or under Transform > Scale > 1, 2, 3. I'll just go ahead and open up the icon. Click and drag to fly it out and leave that there. Let's scale the arm in three dimensions. I am going to start by selecting. Click the 3D Scale button. The first question is, please define the origin.
Let's turn our Point snap on, so we can now find it. This is why it's a good reason to work in the Perspective viewport so you don't pick the wrong spot. So, for all scales, we are going to pick a starting reference point and then an ending reference point. And this could be any two points that you select. So, I am just going to start outwards, and I'll move in to scale down. Conversely, if you move away from the original reference point, it's going to scale larger. So, it doesn't really matter what that is if you are just going to do an eyeball reduction.
So, that's looks about right. I will click again to accept. So, we saw that engineering situation where we have the intersection of the arm and leg. But I am now noticing that this arm looks a little too skinny. So, let's try the 1-D scale, and this is where it's really handy to be in the Perspective viewport. I want to make this 50% wider instead of eyeballing it. So, I need to pick an edge where there is 2 points along the same axis. I want to scale only in 1-D for thickness.
We'll select the 1-D scale command from the toolbar. Pick the object. Hit Enter since we have no more to add. Select the origin as one of the endpoints and instead typing a second reference, I'm just going to type in the scale factor. Notice what the command line says. So, I'm going to do that by entering 1.5 and that will be a 150% increase in width. Now, it will start scaling automatically, but it's asking for the second reference point to give it a direction. So, I am going to click on that second point.
So, let me zoom back out. You can see it's 150% thicker only in that one axis, one-dimensional scale. Let's explore 2-D scaling. And for that, I'm going to turn on another layer for some Robot 2-D geometry. Here we have a gear with a very specific size. Note that it's 19 units across, so that gives us a measurement of 9.5 for the radius. I have just been told we need to upsize this gear so it's 24 across.
So, that will be a 12 units radius. I don't know the exact percentage, but I don't need to with the next method of scaling. We will start with 2-D scale here on the toolbar. I am actually going to pick the dimensions as well. Enter when done. Select the origin. Intersection is selected so this will work just fine. And I'm going to pick the first reference point, so I want to make sure I'm very precise. Pick the edge that is currently 9.5. And you can see as I move around randomly it grows and shrinks.
I am going to type in an exact number that we want to hit, which would be half of 24 or 12. So, the dimensions have updated to verify that. It's now 24 across or 12 for a radius. These text labels are Rhino dimensions, which are able to be dynamically updated, and we will discuss those a little bit later. So, it's just another way to get things larger or smaller with exact precision. Let's take a look at a few more objects and do some 3-D scaling and 1-D scaling and point out some potential problems.
Okay. We have got this bracket here with some fillets already done on these inside holes. Those fillets are running in three dimensions. So, we have got to be careful about this. If we scale in three dimensions, we are fine. So, let's go ahead and do that. I'll pick the 3-D scale, select the bracket, right-click, origin point. For this example, I am going to type in 0.5 so we will get half the size of the original. Now, since I scaled in three dimensions, the fillets still look fine. So, that's the good case.
Here is the bad situation. We have a copy. I am going to scale this in one dimension, and then we'll take a look. 1-D scale, select the object, right-click, origin. First reference, I'll just click on this corner, and I'll type in 0.5 so it'll be half as thick. If we take a look, this are probably not what you want. These fillets have been completely squashed, and they are no longer a uniform radius everywhere. So, the workaround to avoid that problem is to do your fillets last whenever possible.
Pick this corner as the origin. Scale factor 0.5 to be half as thick. I will just make sure I've picked second point in alignment so it goes the correct direction. So, here everything looks fine, and now I can add a fillet to finish it out, and the fillets will be perfectly scaled for the exact size I want without any problems. Scaling objects is very straightforward and only occasionally tricky, but this gives you three different ways to determine the final size. So, you've got the eyeball method just for looks, the percentage method where you know the increase or decrease, and then you have the size method where you input how big it should be when you are done, and not need to worry about the math percentages.
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