Details on curved surfaces 2 : Flow on surface

- [Instructor] In this lesson, we learn how to make detailed or complicated geometry follow along on a curved surface. The command we'll be using is called Flow Along Surface. We're looking at an end result here, just as a sneak preview. This is kind of some blue zipper geometry. Now this was transformed, or flowed, from our reference over here, if we zoom back out. Let's go ahead and turn off the solution layer and focus on how to set this up to work properly.

Also, I'd like to go ahead and do a little practice run here on this sample target surface, let him be a stand-in for the penguin. We'll start the command by going to the Transform menu, and then Flow Along Surface. First thing it's asking is select all the objects. I've got these zipper pieces here, and they are already grouped together, so that'll save me a little bit of time. If not, you can draw a selection box around yours. So that's the only thing I'm selecting, just that one group. Right click to accept. Here comes the tricky part. It's asking us to select a reference point on the base.

So I'm just gonna click here on the lower left corner. Now I need to give it a matching on the target. So even though this is completely deformed, I know from experience it's gonna be somewhere down low, and right along the seam edge. So I'll just select somewhere there. The point here is just to see what happens. Now, as you may not have guessed, it gets really weird. So we have a mismatch in a couple areas. The first one is it kind of turned sideways. So we can actually fix that by first talking about this base plane here.

I've kind of highlighted that its U direction is going horizontal, and the V direction is going this way. So obviously, that has been rotated somehow on this shape here. Let's go ahead and delete that geometry that was flowed. Looks cool, but it's just wrong. Delete key to eliminate. I'm gonna select this object, and we're gonna do a command called Direction, which is on the main toolbar here. Let's click that. Usually, it's telling you which direction the normals are, but there are some other cool settings here. We're gonna swap the Us and Vs.

Doesn't look like much happened, but I'm gonna right click to escape and exit out. And we'll just repeat that last command and see what happens. So I'm gonna right click in a blank area here, flow along surface, select this group here. Looks like I got the plane, so I have to select the thing I want, and the Control to deselect the plane. I just want the geometry of the zipper. So right click to conclude. Again, we've got to pick the base surface, so I'm gonna pick this lower left corner, as before.

Same thing on the target. Now, it's a much better orientation so it's kind of a little more predictable, it's kind of staying in the same angle, doesn't get stretched too much, but it does go all the way around. So that's something else. This is the second problem we're gonna now start to talk about. It takes this surface, and basically deforms it to the final shape, in a sense taking this design geometry along with it. So that means we need to have a closer match between the base and target.

So how does that work with a penguin? Well, it's gonna do the exact same thing and wrap around front to back. But as you saw with the solution, from the beginning of the video, I want it to fit in that narrow little area. So if I quickly switch to a wire frame view, you can see what's happening inside. I drew a simple rectangle and made sure it was the same proportions, two by one. It doesn't matter what the units are. I then projected that to the front. And if we go back to Shaded view, you can see that sitting there right now.

So there's the curve projected onto the front of the penguin. Now if I trimmed the penguin, I wouldn't have any penguin left. So, here's the really cool part of the trick and what makes this whole thing work. I'm just gonna select the penguin body, and that's just the part we're gonna be using, which kind of wraps around, goes up to the head. I'm gonna do a quick copy and paste. So that's Ctrl + C, Ctrl + V. And then I definitely want to hide it away. So you can use the Hide command here on the toolbar or the Ctrl + H is the shortcut, Cmd + H on Mac.

So when I click here, I should only have one left. The other one is waiting, because right now we're about to trim the heck out of it. So let's launch the Trim command right here. Cutting objects is the curve, which is touching, because of the projection. So I'm gonna right click to accept. Then the object area to trim, we want to go outside. So click anywhere around that curve, not inside, we'll get a hole, so just click the outside. Right click to exit. Now we've got a target, which is a better match to the base.

The only problem is, if I turn this guy on, select it and highlight the points on, you'll notice that they go all the way around the body, as if it's still its original size. Not a problem. I'm gonna turn those back off with the Escape, or we can actually just leave them on. The command I want to talk about is under Surface Edit tools, and we're gonna shrink a trimmed surface. Basically, we're gonna lose the ability to untrim in the future. Don't need it, I've got the original I saved. So let's just shrink that surface by selecting it right now, right click, and voila, all those extra control points are now gone.

So this is the total summation of the surface. And, as you can see, much better match for the base. I'm gonna turn the control points off with Escape twice. You can hit the button right here, right click or F11 on PC. What we might want to do is just go ahead and bring back the original. We can do that by right clicking on this light bulb icon here. So we do have two. We have to be careful which one we pick, but we're almost done. Let's go to Transform, Flow along surface.

I like to zoom in here to make sure I pick the right thing. So there is the geometry. Right click to accept. There is the first corner on the base. Now we're gonna go over to the target, make sure we get the smaller piece here. We want the small when we trim, not the overall one, we're gonna keep that for later. And there you go, the geometry has now been flowed across and the distortion has been minimal. Although, there's a lot happening here. This has been very nicely and accurately deformed to perfectly fit.

Let's go ahead and get rid of this temporary geometry that we used to flow. So just make sure you pick the small one that's been trimmed. You can hit Delete. You can also get rid of that original curve if it's in the way. Hit Delete again. So that was the final result to show a little zipper detail on our penguin. I do want to talk about one more thing, and this may be very helpful in your work. A lot of times people want to trim these, or Boolean them together, so we can get a very nice prototype. So what will make that so much easier is if you put your geometry somewhat going through the base so that when it arrives on the target it goes through and the trimming is seamless.

Now if you were to put it right on top of this base, there might be tiny little gaps when it gets wrapped on the surface over here. That's not gonna happen if it goes all the way through. If we come inside the penguin, you can see what's happening. This'll be perfectly easy, and a guaranteed trim. Well that worked pretty well. The key to using the Flow Along Surface command is figuring out where design geometry will end up on the target. If it ends up somewhere weird, then try first to Swap UV, and then second, try copying and pre-trimming the target geometry to get things to go where you want.