N-gons can be a very useful tool when creating a model, they can speed up the process of creating our topology quite a bit and can help us resolve the details of our model, but at some point we'll likely want to fix them as they can cause problems for our topology and may not export properly, so how do you fix N-gons?
Here's how to find and select N-gons:
Next, we'll learn more about Ngons such as, what Ngons are, if they're bad, and a few methods for how to fix them.
Let's dive in.
N-gons are any face that connects more than 4 vertices.
They are usually only seen in 3D modeling tools as they mainly serve as a way to quickly fill in gaps in a mesh. In Blender N-gons act more like a group of faces that look like one continues face.
This is noticeable if we create a N-gon and move one of its vertices, if we look at the resulting face at an angle you may notice the edge of the triangles that define the shape of the N-gon behind the scenes.
N-gons aren't inherently bad in Blender, they can actually be quite useful when we're modeling, sometimes we may want to fill in holes in our meshes and don't need to worry about the topology. N-gons are great for this because it means blender will automatically create all the triangles needed to fill in a section.
While they can be a very useful tool they can also cause us issues, for example if we want to rig our model the N-gons on our model will not deform well, most likely causing weird stretching on our models.
N-gons can also have strange effects when combined with some modifiers, for example the Subdivision surface Modifier may subdivide our N-gons unevenly, again causing weird artifacts. However a subdivision surface modifier will always turn a mesh into an all-quads topology.
In Blender we can create N-gons with any number of sides we'd like. Keep in mind that since Blender handles N-gons like a collection of faces rather than one flat continues face. If you use N-gons to fill in an uneven hole it may result in strange geometry.
As a general rule, Ngon works well as long as it is flat. If we start to change the different heights of the individual vertices, the underlying geometry will shine through, and we will start to have shading issues.
When working with Ngons, you may want to consider using some shading techniques and learn how the normals behave. You can read more about that here:
Related content: How to smooth the shading on an object in Blender?
While Blender has support for N-gons they may also cause issues if we try to export them.
While most formats will usually automatically triangulate our meshes, some do not which could result in faces not rendering properly in some other applications. For example, game engines are unlikely to support N-gons and some 3D Modeling tools may not support them or have limited support.
Considering how easy it is to create N-gons and that they can be hard to spot you may need a way to find them quickly. To find them, follow these steps:
As you can see, all of the N-gons on the model are now selected, of course this will also work with larger meshes.
There are other ways to select all N-gons but I find this to be a fast and easy way.
While N-gons might be a useful tool, we may also want to fix them later on. Below I've listed a few methods for how to do so.
The first method we'll go over is to simply triangulate the whole mesh. Follow these steps.
This method is one of the most simple ways of fixing N-gons but it is not optimal for preserving topology, if we want to do further work on our model, having all of the quads converted to triangles can make working with the mesh much more difficult.
The next method is to triangulate only the N-gons on our mesh, we can do this by first selecting all of the N-gons on our mesh and then triangulating them.
This method will work pretty well for fixing N-gons but isn't the most optimal if we're trying to maintain an all quad mesh, and sometimes Blender will triangulate N-gons in a strange way that results in weird, jagged shapes on our models.
The last method we'll go over is the most hands on and allows us to control how our N-gons are divided, for this method we'll be using blender knife tool to cut up our N-gons into Triangles and Quads.
Related content: Blender knife tool tutorial
Then repeat this process for the rest of the N-gons on your model until none of the faces connect more than four vertices, this method combined with using Select Faces By Sides can help you find and fix any N-gons on your model.
Apart from the Knife tool we can also use a combination of tools and selections. You can learn more from these articles.
Related content: More than 30 Blender modeling tools explained
Related content: How selecting works in Blender
One more topic I'd like to touch on is turning N-gons into quads, this is important for maintaining clean topology on our models, while I won't be going over all the general rules for maintaining good topology for this topic, I will go over how I kept all quads for the example shown throughout this article.
I suggest using the knife tool for this process since it gives us control of how the N-gons are divided but you can just triangulate the N-gons if you'd like.
With the N-gons converted to triangles and quads the next thing to do is convert any triangles in our mesh to quads.
For this example, it was fairly simple, since the resulting mesh had an even number of triangles, I was able to just pair them and drag the vertices around to minimize stretching, though in your mesh you may need to reroute some of the geometry to be able to turn everything to quads.
Here is an example of what that could look like.
N-gons can be very useful when we're creating a model's geometry, but they also need to be managed properly so that we don't end up creating messy geometry.
Blender comes with many methods to help manage N-gons and as a result we can take advantage of their utility as well as being able to fix them when we want to clean up our models.
Thank you for your time.