Dave's intersection technique: A potato chip - Rhino Tutorial

- [Instructor] We start this video series with one my favorite modeling strategies, which I will call, Dave's Intersection Technique. It's powerful, but also pretty simple, even though it can be a bit tricky the first few times you try it. We'll start off with this simple, potato chip shape, also called a saddle shape. These are also known as compound curvature, which just means that they curve in two different directions. With my intersection technique, we'll start off by picking two different views that are the most descriptive, and then figure out a way to have them intersect each other. Now these two views can be represented by either curves, or surfaces, so we'll do one of each in the next example. Let's take a peek at the final shape, here in the perspective view port. And what a lot of beginners do, is they'll look at a shape, and they'll try to trace all the edges and/or the isocurves. So that can actually take you a lot longer, and make for a less clean result. So again, the focus will be making two opposing, or different sided profiles, intersecting them. So if I were to analyze this, I would probably say this view here, which might be from the top, and then on the side, we should have a very simple shape going the opposite direction. Let's start off by drawing a curve in the right viewport, and go ahead and highlight this, and I'm going to use a very simple control point curve, over here on the left side of the main toolbar. So I'll just draw a couple points here along the way. And as usual, you probably have to come back, and make a little bit of tweaking. I'm going to turn the control points on with F10, and then we can drag these around. Or, if you have too many, you can also hit the delete button. So that looks fairly simple. Let's go ahead and turn this off, with the F11 keys, and then I'm going to maximize perspective by double-clicking on the label. So here is the curve we just drew in the side view. Now I like to leverage my geometry whenever possible, so I'm going to go ahead and just copy this a couple times. Highlight and then Control + C to copy, Control + V to paste, and drag that extra copy off to the side. I did hold down Shift, that's why it went perfectly sideways. Same thing other direction, Control + C, Control + V, and drag the copy off to the side. Now these are all in a straight line, so it's not very organic. In fact, they would look just the same as an extrusion. So let's pick this curve here in the middle. We'll go back one more time. Here we are at the side view, so I'm just kind of drag that up in the air. So that should give us a nice, organic, lofted shape. Let's go ahead and look for that command. It's under Surface, Loft. I'm going to pick the three curves in a row. You can also check the command line if you're not sure when, or what to do. You will right-click, or hit return to complete the command, and then you have a few options here. I'm going to go ahead and accept all of the defaults, and there is a nice, clean loft shape there in the perspective viewport. Let's go ahead and get the profile going the other way. We can do that from the top view here. I'm going to turn off my title layer, just so it's not in the way. So I can just draw a real quick, simple shape, again, using the control point curve. I've got a few of my Osnaps on. I think endpoint is going to be all that I need, and probably turn off near. And just go around the outside here, just come up the middle. Go around, and then hopefully you're going to snap at the end, that's why the Osnap is on. Now it looks like it's nice and flat there in perspective. Let's go ahead and maximize this. If this curve snapped to something in the scene, and was jiggling up and down, you can always flatten out very easily with the Transform, Project to Cplane. However, this is flat, as we already drew it. So, we're going to just jump straight ahead to the trim command. Now, a lot of times, you'll want to, on more complicated shapes, project this straight up so it hits the surface. However, both this surface and the curve are fairly simple, and with this construction plane being flat, it will do the projection automatically. So we could do this in top view, or perspective view, either will do the same. And again, it's all dependent on this construction plane direction. So here's the trim command. Start that going. It says, "Select Cutting Objects", that will be the curve to cut. Right-click to accept, and then I'm going to make sure I click somewhere on the outside. If I click here in the middle, I'll end up with a hole, so I want to come over here on the outside edge. It will subtract all the stuff on the opposite side of that curve. So there is our potato chip shape. I'll go ahead and turn a title text layer back on so we can summarize. And I'll say, this is a pretty simple example, but it works well to introduce the basics. Remember to capture the form from two different directions, and if you have any trouble, just draw a sketch, followed by several ortho views, like the front, or top, or side, and give it a try.