Why You Need to Learn Topology

Added: 2026-05-12

[00:00:00]So, a lot of people are arguing over whether or not you need to learn about topology, whether or not topology actually matters. So, in this video, I'm going to show you a little example of when topology matters and when you can't really go without it. And then you're also going to see when it doesn't matter. In this case, we're going to talk about this PUBG helmet, which we've been modeling the last couple of videos.

[00:00:17]And I ran into this situation when I was modeling the visor over here in the front when I had to cut the hole where you fit the glass. So, over here on the side, I recreated a simple version of this visor just so I can demonstrate to you how this stuff works. And here's the situation that we're in right now. So, we have this curved surface over here in the front. Luckily, this one's only curved around one axis. If it was curved around two axes, then it will be a little bit more complicated. But here's the problem. See, right now, we have to cut a hole in this surface in the front here, which looks like, well, the hole that you can see back here. As you can see, the hole has these round corners, and that's where things get a little bit tricky. Because if you're a beginner at Blender, when you think about cutting holes, the first thing that probably comes to mind is using the boolean modifier. Let's try that. And then I'm going to show you why this is not going to work properly and why you have to use topology here. So if you want to cut a hole here using the boolean modifier, we would start by creating a cube over here in the front. We would scale that cube down to make it a little bit thinner.

[00:01:06]Then would scale it up on the y-axis like this. We want to make sure this cube pushes into the curved surface as you can see right here. And then once we done that, now you can take this object where we want to create the hole. You're going to go to the modifier section, add modifier, generate, and generate a boolean modifier. In the boolean modifier, you're going to target this cube. And then of course before we apply this, we also want to bevel these corners right here. So we select these edges, we press Ctrl +B, we scroll up a couple of times. And there we go. Now we got our beveled rounded corners. So now we can apply the boolean modifier to this object. We can get rid of this cube. And now we have this hole here.

[00:01:38]Now, currently this is just a flat surface. It's not supposed to be that way. The inner part is supposed to be curved. That's not really a problem because we can just cover the inner part using some of the edges from the top here. So maybe we can just duplicate those, push them backwards, and extrude them down like this. That's not the issue here. That's the simple part. The issue here is that now because of the way we cut this hole here, we [ __ ] up the geometry on this mesh. So now if you look over here on the side, we have this face which has a very weird shape. This is called an engon. It's a face which has more than four edges around it. In this case, it's a concave engon, which means it has vertices with inner angles greater than 180°. And this is bound to give you all sorts of problems down the line. This is just bad topology. Now, this is not an issue of principle because somebody said we have to have quads only and we can't have engones.

[00:02:21]Engon are not necessarily an issue all the time. I'm just saying in this case they're an issue. And let me show you why. Because on this particular model, we want to use some smooth shading because, well, this part over here is supposed to be smooth. We don't want to see these lines. So, what we're going to do is go to object shade auto smooth.

[00:02:35]And that's going to make those surfaces nice and smooth. But if you look over here, you're going to see that we got some issues. We got some shading artifacts. If you look closely, we got these weird lines here. If we go up here and we switch to a different math cap, they're going to be a lot more visible.

[00:02:47]Now, you might think to yourself, well, it doesn't look like that much of an issue. hardly anyone's even going to notice this. Well, yeah, that's probably true in this example, but there are going to be examples where this is going to be very noticeable. So, you have to know how to avoid these kind of issues.

[00:02:59]And in this case, I don't want to have this line. I want this to look nice and smooth. And before we can fix this, we first have to figure out why this is happening in the first place so we can avoid that in the future. So, we're going to move over here to the side where we got a very simple example and we're just going to use this so I can explain to you how the mechanism works.

[00:03:14]We just have this simple angle. I took a plane and I extruded an edge. So if we go up here to object shade smooth when you use smooth shading that smooth shading is contained by the surrounding edges around an edge. So as you can see here we have this corner and then when we add some loop cuts over here that smooth shading is limited to the area inside those loop cuts and there's no smooth shading beyond that. Everything looks the same as it did before. The smooth shading only takes effect on this corner right here. So the main thing you need to understand here is that smooth shading takes effect only when you have an edge with an angle. When you have an edge which does not have an angle or when you have an edge connecting two faces which have the same normal lines or rather normal lines which are perfectly parallel then the smooth shading is not going to spill over that edge. But if we take this edge and we push it down well now this edge here becomes angled. So now we also get a little bit of smooth shading on this side. You can't really see it because it's going all the way here. But if we add another loop cut here you're going to see that there is smooth shading between this edge and this one over here because now this edge here is angled.

[00:04:09]Now when you have an engon and you apply smooth shading to an edge which is part of that engon. So for example we have this surface right here with a big engon. We have another face down here.

[00:04:18]This edges at an angle. We go to object shade smooth. That in itself creates all sort of shading issues. For example, right now you can see we got these weird lines. We got something else going on back here. Then there's another weird shading issue going on in the corner down here. Basically it's all [ __ ] up.

[00:04:31]We can't have engones and smooth shading. They don't work well together at all. Engon also give you all sorts of problems when you use a subdivision surface modifier. For example, look what happens if we apply a subdivision surface to this object. So the issue here is not that we have engones. The issue is that we have engones at an angle with smooth shading. And that's exactly what's happening down here. We have this big engon. There's an angle over here. We got smooth shading. And that's why we got this shading artifact.

[00:04:54]Now, before I show you the right way to create this shape, let me just show you something over here on the side of my helmet. You can see that we also got an engon over here on the side, but that doesn't cause us any issues. There are no shading artifacts over here. That's because we marked this edge over here as a sharp which means there's no smooth shading on this edge. So we don't have that smooth shading and engon combination which causes all the problems that we just talked about because when we mark this as a sharp that's effectively the same thing as completely separating this edge from the surface up here which means the smooth shading simply does not exist on this edge at all. So now here's the right way to create this shape that we're trying to create here. So let's create this one more time. I'm just going to create another version of this object right here. The name of the game here is we have to use quads only because well we're trying to cut a hole on a curved surface and in that case we can't have any engones. We can't have any triangles. We got to use quads. Now in this case first of all since we want to create a nice round edge here we're going to need a lot more geometry on this object. So I'm thinking I can go w subdivide. Then I can take this edge segment over here and I can dissolve it.

[00:05:51]And then just to make this a little bit smoother because now we just subdivided.

[00:05:54]We didn't make the edges nice and smooth. I'm going to take these edge loops here. I'm going to use my loop tools to make them a little bit softer and a little bit smoother. Maybe I'll set that to linear and turn up the count here. Now everything is nicely distributed as you can see right here.

[00:06:06]And now we're going to add some loop cuts over here. So we turn everything into little squares. That's always the way you want to do it when you're trying to work with clean topology. Now I know this turns up the polygon count quite a bit which is not optimal if you're trying to make game assets. And we are going to be able to dissolve some of this geometry later on. But there's also no way to make this look nice and smooth unless you add a little bit of geometry.

[00:06:24]So you have to find the right balance.

[00:06:26]You want to have enough geometry so you can create what you want to create, but you also don't want to have too much to where your model just has 6 million polygons because if you got that many, then maybe you want to reduce that to something like 271,000. But anyway, here's how you create the shape. And this is where you have to use some slightly more complicated techniques, but there's no way around it, guys. You got to learn this [ __ ] if you want to be able to create models properly. So, in this situation, we want to have a hole which has round corners. And the way I like to do this is to first create a little circle up here. Then I'm going to take one quarter of that circle, delete everything else. Never mind talking about it. Let me just show you. Here's how we're going to do it. We want to turn this little surface into a circle.

[00:07:00]So, that's a 4x4 surface. That's going to be the corner of our visor. We're going to insert these faces with I and we're going to use our loop tools to turn this into a circle. And hopefully that works because sometimes there's a bug here where it just messes everything up. But once you create your circle, you also want to uncheck flatten because you don't want that circle to be flat. You want it to follow the curvature of the surface. So, look at this from top view.

[00:07:20]This is the default when you have flatten checked. As you can see, the circle is flat and it does not match the curvature of the surface. But when you uncheck that, it looks a lot better. So, this is what we need. And then we delete the faces in that circle and we select this little loop and deselect this quarter and delete all the other faces around here. And now the rest is very simple. We just have to clear out everything else from the inside of this surface. So, we're going to take all these faces from over here. We're going to delete everything except the frame and this little corner. And now, we just have to place this little corner onto all the other corners and fill in the remaining geometry. So, we're going to place the 3D cursor into the middle of the object. Maybe we can place it right over here between these four corner vertices. That's exactly the middle. And then with the pivot point, set the 3D cursor in face select mode. We're going to take this little corner, shift D, right click, scale it to minus one on the Z-axis. And then take everything one more time. Shift D, right click, scale it to minus one on the Y-axis to mirror it to the other side. And of course, now since we inverted the geometry, we have to correct our normals with shift N. And we also have to merge our vertices by distance. So my shortcut for that is shift W, but for you it's going to be m merge by distance. That's just going to connect these vertices over here where we got double vertices. And now we just have to fill in the sides. So we're going to use our 3D cursor over here. We place it onto this little vertex. We take this geometry from the top.

[00:08:30]Extrude, right click, scale to zero on the Z-axis. Do the same thing at the bottom over here. And now on the sides, it's a little bit different because now you have to take this geometry, extrude, right click, but you're going to scale to zero with shift Z because you want to scale it on all the axes except the Z-axis because of course, well, you don't want it to shrink down on the Z-axis. You just want to shrink down on the X and the Y. So you set that to zero. And we do the same thing one more time over here on the other side. And there we go. Now we got our frame and the topology is clean. We have some edges over here which we can dissolve because they serve no purpose. And the way I know that is because if I dissolve these edges, they don't change the shape of the object. They don't create any artifacts. They don't do anything for us. If we were using the subdivision surface modifier, maybe they would be a little bit more important because they would act as supporting geometry for this corner right here. But we're not using the subdivision surface modifier.

[00:09:16]So, we really don't need those edges for nothing. And now, if we want to extrude this inwards, we're going to take this surface over here. We're going to go to face grid fill. Blender can be a little bit [ __ ] with this tool. So, he can't figure out how to do this automatically. So, we're going to have to tell him if we go up here and we check statistics to see how many edges we got. We want to select one quarter of this inner loop. So, we're going to select the top quarter. You can see we got 60 edges right there. So, that's what we're going to use for a grid fill tool. You want to select this. Go up here to face grid fill. Set the span here to 60. That's not the problem. The problem is that we still have these edges over here on the other side. So, the number of edges is not equal on the two sides. Anyway, now we try again face grid fill. You can see you figured it out pretty damn well on his own, but it's going to be a little bit better if we set this to 60 and adjust the offset a little bit. And once we got that, now we can go alt e extrude faces long normals. extrude everything inwards to create this inner surface. There was probably an easier way to do that, but now it's too late. We can delete these faces. And there we go. Now we got a frame. And you want to have a surface similar to this one on the inside of that. And there you go. Now, we created this with perfect topology, so we're not really going to get any shading artifacts. If you go to object shade, auto smooth, and you look closely at this area, you're going to see it behaves as you want it to. If you really want to have a closer look at this, you go up here to your mat cap. You use a zebbrush shed, and then you check to make sure there's no folding or bending or anything else. And as you can see, that looks perfect. So that's an example of when you have to use topology.

[00:10:33]There's no way around it. And over here on the side, you saw another example where you don't have to worry about topology. Well, you still have to worry about it to a degree, but you don't have to have perfect subV workflow all the time. You only need to use good topology when not doing so would cause you some sort of an issue. So that's it guys. If you want to learn more about topology, I got a free topology guide which is going to explain this in a little bit more detail in the description. If you want to learn a million other Blender tips like this, then check out my Blender masterclass course in the description.

[00:10:56]Let me know down below what you want to see next.