Join Dave Schultze for an in-depth discussion in this video Organic modeling: Two-curve taco shell, part of Rhino: Tips, Tricks & Techniques.
- [Instructor] Thanks to Rhino student Evan for this demo idea. The taco shell you see here was made with only two curves, amazing! The process I will show you is more about strategy as opposed to drawing a large amount of complicated curves. So let's recap that process, and I've mentioned this before, but we always want to use the minimum number of curves and keep those curves simple with the minimum number of control points. I also like to build some things bigger than needed, and that makes it easier to get the original size by coming back and trimming or splitting to get the final shape.
Okay, let's review here. We'll zoom out. I said two curves and there they are. I'm going to select both of these and turn the control points on. PC, you can hit F10, or on other computers you just hit the points on here. And you'll see that those are pretty darn clean, not a lot of points along the curve. Turn those points back off. Also notice the configuration. These two curves have overlapping ends. The reason I do this is they can have a positive overlap for later trimming.
You'll see that in just a minute. Let's get a few more curves out of here. Remember, we only made two. The rest are just copies or surface commands. I'm going to select this center curve right here. And control+C or command+C on the Mac to copy and then control+V to paste. I'm just going to drag that off to the side, not even worrying about where it's going. I'm going to make one more copy, do the same thing, control+V to paste. You should have an extra copy on the other side when you drag it out.
Okay, just a heads up, we're going to loft these three curves right now, the reason being is they're in a perfectly straight line. So we just would've created an extrusion, just a little more difficult way. The key to this process is to make these three curves a little bit different or move them up or down or both. Let's switch to other view ports. So I'm going to take this one on the far end and just lift it up a bit. And this one goes up an ear also. And maybe we'll make the center one, we'll turn the control points on with the points on or F10.
We'll make that guy just a little bit wider. They're not so consistent though, there's a variation when you're doing organic shapes. That should be plenty. I'm going to go ahead and hit escape a couple times. That's another way to turn off the control points. And I'm proceed to loft, so I pick one, two, three in a row. That helps avoid twisting though, if you select them in a certain order. We're now going to go to surface loft, and we should get a really clean result here.
That looks pretty good. Just hit okay and accept. Now I want to go ahead and trim this back, and I'm going to do this in the right side view. Here, if I switch over to wire frame you'll see quickly that this curve crosses over the other surface, and that's the reason I had the two ends extend past each other. Let's go back and turn it over to shaded just like we had. So one cool little technique to share with you is, instead of having that curve in the center, somehow extruded or projected and then trimming.
Since they're both fairly simple, I mean the curve and the surface we're trimming. We can go to one of the view ports and just try a trim command there. Usually Rhino just knows how to do the job and it'll happen right away. So I'm going to select over here on the main toolbar, trim. Cutting objects is the curve. Just the one, so right click to accept. And the next place we pick will get chopped out. So we want to go here to the outside, click and right click to exit, and there you go, we've got the nice clean shape and organic flow trimmed back, and it looks really clean on the edge.
We didn't have to make any extra operations. Just trim from the side view where it looks like it's going to intersect. Okay, I'm going to jump to fullscreen here. You can double click on the perspective window. See a little bit better what's going on. So this taco shell needs a little bit of thickness, so let's go ahead and do an offset. So I'm going to select the surface ahead of time here. I'm going to surface, offset surface. I'm going to select a distance of six, so just type that in right there.
We're going to leave everything else alone except for the direction, notice that the arrows are pointing. Kind of an assumed normal direction. Whenever I offset, I try to usually go outside. If you offset inside, it tends to get a lot more complicated and, in extreme conditions, can self-intersect. You'll see a little bit of loop inside. So I always try to, if possible, offset going out. So I just click on the surface here, and notice the arrows will flip the other way.
Or you could just click on the option up here, flip all, it does the same thing, just a simple toggle. I'll right click to accept that. And we should have the outside surface there. So we've got the two parts of the shell, we do need to close it up. A lot of people would do the offset with the edges included. I think that's way too sharp, so I want to share with you a really cool way to blend these back together. It's a little counterintuitive, because these two surfaces are pretty much parallel. Most people think of a blend as having to trim back something so the blend can fill it back in.
But parallel surfaces can actually be blended really effectively. Let's go to surface, and then blend surface, right here. Hopefully these are clean enough that we can get the edges selected just with one click each. So I'm going to click inside edge here, goes all the way around. I want to exit this now, or accept it I should say. Right click, and then ask for the second edge. So there you go. Each of those two edges were just a single selection. That tells me it's a very clean surface.
Now we have these two seams over here. They should usually line up, especially if you did an offset, because it's really kind of a copy of the original one. So as long as those two are aligned, you're in good shape. I'm not going to move those, I'm just going to right click to proceed. We do get a little bit of a preview of the curve shape here. However, it might be easier for you to understand if you just click preview and we can get to see the whole surface all the way around, not just that one little curve profile. Now, another thing I like to do is those will get a little bit distorted as they go around sharp corners or larger corners.
They get different. So I'd like to click same height. So you'll notice it gets back to kind of a consistent height all the way around. So you can make that height larger or smaller. If you go ahead and lock these two, you can have them move together, so that comes out just a little bit. So you can play around with that a little bit. The thing I want to talk about now is a little bit of twisting as it goes around the corner. You'll notice that if this were train tracks, you'd want the cross curves to be perfectly opposite each other.
And it's, one side's getting ahead of the other, and that can cause a little bit of deformation. So a lot of commands will let you add additional shapes along the way. I'm going to select this option right here. And then it's pretty loose and flexible. I'm just going to click anywhere I feel like, I'm going to maybe come down to somewhere low, and then just go straight across. If you can turn on perpendicular you'll see it snap right there. That's a good way to know that it's the shortest possible distance. So I'm going to click on perpendicular and activate that now. And you'll notice when I click there, all the other profile curves kind of realign in the immediate neighborhood.
They do get a little bit of an alignment as you go farther around, so we just keep adding a few more shapes. So I want to probably do the same thing right over here. It goes pretty quick once you kind of get into the groove of it. So just click and get the perpendicular snap going. Hit okay. And there you have it, you got the two surfaces beautifully blended around the edge there. These are separated, so if you want this to be all one piece, you can click the outer shell and the inner shell just by shift adding.
And then the little edge we just made. And those should now join together seamlessly. You can use the puzzle piece or control+J for a shortcut. And finally, it may look a little more complicated but it's actually very smooth and organic. And we can kind of preview that by just turning off the iso curves over here on the properties. Select visible. So with that deselected, all those complicated iso curves go away. And we can enjoy the beauty of our super clean, organic taco shell.
So we made this clean yet organic surface with only two curves. We then leveraged those with a short sequence of commands. If you haven't realized this, this process helps you build things faster and cleaner. And more importantly, you can change it just as quickly and easily, and then continue rebuilding until it's a perfect design or a delicious taco shell.
- Building and detailing a space helmet
- Making a flexible duct
- Building details on round pipes
- Modeling organic objects
- Using the SrfSeam command to move seams out of your way
Skill Level Intermediate
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