Join Chris Reilly for an in-depth discussion in this video Making surfaces with sweep commands, part of Learning Rhino for Mac.
- Let's talk about creating surfaces using the Sweep commands in Rhino 5 for Mac. I've opened up surfaces-sweeps.3dm from the Example Files and here, we've got a few different sets of curves and surfaces and to work with. So we'll look at making surfaces with two similar Sweep commands: Sweep 1 Rail and Sweep 2 Rails. Sweep 1 makes a surface that passes through one or more profile curves and those act as cross-sections along with one rail curve that defines a surface edge. And Sweep 2 behaves almost exactly the same way, only it has two rail curves that define the surface edges.
So we can find these commands under the Surface menu or through the Surface icon or by typing into the command line. So let's start with these curves here and these are located in the Sweep1-A layer. So, right now, I'll just go ahead and toggle off the Visibility on the rest of these layers so we can see what's going on a little bit better. I'll maximize my Perspective viewport by double-clicking and then just pan over a little bit and zoom in.
Okay. So, we have four curves total here. We have one, two, three cross-section profiles and then our rail. So let's just go ahead and do a simple Sweep 1 Rail on these curves, so I'll go to Surface, Sweep 1 Rail. Now, Rhino's prompting me to select the rail. So I'll go ahead and click to select the rail. And now, it's asking me to select the cross-section curves and here, I want to make sure that I do these in order, so I'll go one, two, three, and then when I'm done, I can either press Enter on the keyboard or just click Done.
So now, I'm being prompted to adjust the seam point and since all three of these profile curves are closed, the swept surface will also be closed in one direction. So, this means somewhere in that surface, there will be a seam where it wraps back onto itself and I can specify where that seam is, either using these command options here, so the Flip, Automatic, or Natural, or by manually clicking and dragging these points in the viewport. So for this one, I'd like the seam to run right along the top middle of all three of these profile curves. So, with my Midpoint object snap activated, I'll just go ahead and click to adjust those and snap them right to the midpoints of each of these profile curves.
And this last one is already in the middle, so that's just fine. Then when I've got the seam where I want it, I can either click Done or hit Enter on the keyboard. Okay. Now we see the Sweep 1 Rail options and I see some settings that look similar to what we saw in the Loft command. So, I have a Style setting, and this determines the orientation of the profile curves to the rail. So, Freeform maintains the initial angle of the profile curve to the rail throughout the whole sweep, and these other Roadlike options, calculate the orientation kind of based on the tangent of the rail in combination with one of the orthogonal direction.
So we have Top, Front, Right, those are your orthogonal directions and many times, these options look exactly the same. Whoops, that one's different. We probably don't want that one. So for now, I'll just leave this on Freeform. And again, just like with Loft, we have the option to align the shapes. If the directions of the profile curves are inconsistent, we can also rebuild or refit the profile curves or use them just as they are. So for now, I'll just leave this on Do not simplify. We also have the option to refit just the rail curve, leaving the profiles alone.
So for now, I'm pretty much just going to leave all these on the defaults and go ahead and click Sweep. So I can say we got a pretty interesting surface here and I can see that it's transitioning from the profile curve that's kind of pointed at the top to these ones that are capped. I get this nice transition along the course of the rail where we're sort of slowly transitioning from pointy to capped. Let's try another Sweep 1 Rail, and this time, we'll explore a couple more of those command options. So, I'll go ahead and activate Sweep1-B and toggle Visibility off on Sweep1-A.
So I'll go ahead and do a Sweep 1 with these curves. So, Surface, Sweep 1 Rail. This is my rail and these two are my cross-section curves. Okay, and for this one, I don't really care too much where the seam goes, so I'll just leave it on the default and click Done. And so this time, we'll look at this Global shape blending option. So, let's enable this and we'll see what happens. So I can see, as I toggle Global shape blending on and off, the Sweep changes pretty considerably.
And so I notice that with it activated, the curvature changes at a constant rate over the course of the sweep. When it's unchecked, the curvature's kind of weighted towards the closer profile curve, so we can see on this end, it's much smaller. On the other end, it gets pulled much larger. So I'll leave this checked for now and click Sweep. Let's try one more with some slightly different inputs. So, I'll go ahead and activate Sweep1-C and turn off Sweep1-B.
Just as with some of the other Surface commands we've looked at, Sweep commands can also use surfaces edges for their input curves. So let's try this example where we'll sweep this profile curve along the surface edge, which will be our rail. So I'll go ahead and do Surface, Sweep 1 Rail. And this time, our rail is the edge of this surface. And this is our cross-section curve, and we just have one. Okay. I'll click Done. I'm going to deactivate Global shape blending and just leave everything else on the defaults for now.
Go ahead and click Sweep and we'll see what we have here. And notice that as we transition from one surface to the next, there's kind of an abrupt change in curvature. I can actually see sort of a seam here between the two surfaces. So, let's try that one again. I'm just going to hit Command Z to undo. And we'll look at some more command options that can deal with curvature. Surface, Sweep 1 Rail. Our surface edge is the rail and again, our profile curve.
Click Done. So when we use Sweep 1 with a surface edge as a rail, we actually get an additional style option down here at the bottom called Align with surface. Let's select that and see what changes. So notice, especially right here on this edge of the surface, I get a big change. So if I go back to Freeform, I can see it's a very straight transition. If I say Align with surface, it kind of follows more closely to the surface that we're pulling the rail from. So I'll go ahead and click Sweep with the style set to Align with surface.
And notice how the curvature of the swept surface now aligns much more closely with the source. It's much smoother transition between the two surfaces. Now let's move on to sweeping with two rails. So I'll go ahead and turn on Sweep2-A in my Layers panel and toggle Visibility off on Sweep1-C. I'll also set my shading mode to Shaded.
And I notice my rotation is a little bit off, so sometimes if it's a little bit funky, like it is right now, it's helpful to place the camera target. You can do that by just right-clicking in the viewport title and under Set Camera, Place Target. And just click right about the center point of where you'd like the rotation to happen in the viewport. So I'll click right there and now, I can rotate right around those curves we'll be working with. So we'll be doing a Sweep 2 Rails with this curve. So I have one rail, two rails, and my cross-section profile.
So let's go ahead and pull that up. I'll go to Surface, Sweep 2 Rails. I'll select my first rail, my second rail, and it doesn't matter what order I select those in, and onto the cross-section curve. I'll go ahead and click Done. And I see that Sweep 2 Rails has a similar set of command options to Sweep 1 Rail. So I have the same cross-section curve options here where I could rebuild or leave the curves alone. I've got a few additional checkboxes here and then down below, we have a set of rail curve options that we'll look at in the next couple of examples.
So, what I'd like to look at here though is this Maintain Height command option. So, let's just slide this over a little bit so we can see what's going on here. Let's see what this looks like with Maintain Height unchecked. Okay, and that should be the default setting to not use Maintain Height, but you can see without it, the wavy rail curves kind of make that profile curve undulate up and down, so we get these little humps along the course of the sweep and that might be what we want. We also may want to maintain that height, so if I check that again, the check Maintain Height, I can see that the sweep respects the original height of the profile curve.
And off to the sides, it still maintains that kind of undulated shape that we get from the rail curve. Okay. So I'll go ahead and click Sweep and we can see what that looks like. So again, pretty interesting shape. Just from a couple of simple rail curves and a profile curve. One thing I've noticed though is that the surface is pretty complex, so I get lots of these isocurves here. And we have some options for controlling how complex the surface is. Sometimes we don't really care. Other times, if we're going on to edit later on, we might want a bit of simpler surface.
So, I'll go ahead and hit Command Z to undo and let's try that Sweep 2 Rails again. This time we'll look at one additional command option. So, Sweep 2 Rails. First rail, second rail, profile curve, click Done. So this time, I'll uncheck Maintain Height and I'll take a look at the Simple sweep option here. So when I check this, notice what happens to my isocuves. I get many fewer isocurves. So, the Simple sweep option won't actually always be available, but since our profile curves endpoints are right on top of the endpoints of each rail curve, so if I zoom in a little bit, I can see, so, since those meet up exactly, we can ask Rhino to build a simpler surface that's based exactly on the control point structure of the input curves rather than kind of making a more complicated approximate surface.
And this gives us more control over the point structure of the final surface and sometimes, that's really important. So go ahead and click Sweep and now, we have a nice undulating simple surface. Let's take a look at another two-rail sweep. So I'll go on to layer Sweep2-B and toggle off Sweep2-A and notice with this one, the rails actually converge to a point. So I have one rail, two-rail, and two cross-section curves. And with these, I'd like the same convergence to happen with the surface, so I'd like the surface to actually come to a point here at the end.
So let's take a look at what happens when we do a Sweep 2 Rails with these curves. So, Surface, Sweep 2 Rails. First rail, second rail, and then my first cross-section, second cross-section. And if I click Done, let's see what happens. Well, okay. Not quite what I wanted. I can see that the surface is stopping at the second cross-section. Rhino's getting a little bit confused about what it should for this second part of the Sweep, so let's cancel for now. What I need to do is to tell Rhino to continue all the way up to this point.
I can do that with one of the command options. So let's go to Surface, Sweep 2 Rails. First rail, second rail, and then to my cross-section curves. So I'll do one, two, and then I need to do one additional step here which is to activate this Point option. And now, Rhino's just asking me to pick a point where the sweep should converge to. So I'd like to snap right to the endpoint where those two rails intersect. So, I'll go ahead and turn on my End object snap.
Snap right there. So I can see now with that Point command option, I can continue to sweep all the way to the end where the rails converge. I'll click Sweep to finalize. Pretty cool. So now, let's do another Sweep 2 Rails. This time, between two surfaces. So I'll go ahead and toggle off Sweep2-B and toggle on Sweep2-C. So just like with the Sweep 1 command, we can also use surface edges as our input rail curves.
So here, we'll be using this surface edge and this surface edge as our two rails and then this curve as our cross-section profile. So I'll go ahead and activate Sweep 2 Rails. That's my first rail. That's my second rail. And this is my cross-section. And I'll go ahead and click Done. And let's just slide this over a bit, zoom in so we can see what's happening. Now, when we work with surface edges as inputs for the Sweep 2 command, we get some additional command options that kind of control how our surfaces line up.
So, here under Rail curve options, I can see sort of this grid of radio buttons with Position, Tangency, and Curvature for both A and B. And A and B are each of our rail curves and I can see in the viewport which one is which. So this one is A, with the little A label. That one's B. And the three options here for each A and B, those control the smoothness or the continuity of my new surface relative to each of the input surfaces. So, if I select Position for both, the new surface edge will wind up with the rail curve, but even though they're in the same location, if I look closely here, I can see the transition is a little bit abrupt, especially here, I get this pretty hard edge.
I can see that the surfaces are really kind of going in two different directions. So if I'd like a smoother transition, I could also change to Tangency. So let's try that for A. And with Tangency, the surface edges line up in the same position and they continue on in the same direction. So I can see I get a little bit of a smoother transition here with tangency on the A rail. And I could try that for B as well and I can see that transition just gets a little smoother there.
So if I want to, I can go even further and try Curvature which sets the position, the direction, and also, the radius of curvature to be the same on both surfaces. So, this gives us a very smooth connection between the two. So let's try that for A. So I can see that changes the surface quite a bit going from Tangency to Curvature. And as we do that, we're adding more and more constraints into the swept surface. So, sometimes it becomes impossible to have curvature continuity between both rail curves. So you can see, if I switch the Tangency on B, also to Curvature, then A swaps back to Tangency.
So, looks like we can't have both at the same time here. So, what I'll do for now, I think the best way that it looked was Tangency on B and Curvature on A. And I'll just click Sweep. And that looks pretty good. And if I change back to Rendered mode, I can see that's a very nice, smooth transition. I really can hardly see a seam on either side there, a little bit right here on B. So, that's an overview of creating surfaces with the Sweep commands in Rhino 5 for Mac.
- Installing Rhino for Mac
- Viewing a 3D model in Rhino 5
- Manipulating objects with commands
- Creating curves, surfaces, and solids
- Applying transformations to 3D objects
- Creating unique shapes with Boolean operators
- Snapping to objects and planes
- Prototyping a 3D model
- Lighting and rendering