When creating meshes in Blender we will often need to consider poly flow and best practices for creating geometry, it commonly recommended to keep our meshes quad based, but why is this?
Quads are preferred to triangles because they're easier to work with and in general have more consistent results such as smoother and more evenly distributed Subdivision Surface modifiers, though triangles can be useful in some cases such as a complex mesh where adding an extra loop to convert a triangle to a quad wouldn't be an option.
In the rest of this article, we'll go over more details about triangles and quads as well as the reasons why we might want to use triangles instead of quads.
When we say tris in Blender, we mean triangles. They are any faces that connect exactly three vertices with three edges.
Any geometry can be represented with triangles. They are an essential building block of any 3D mesh. Under the hood, all faces in a mesh are recalculated as triangles. But these triangles are hidden from us, but they are what the renderer sees.
But, when we talk about triangles and topology, we talk about the topology that we can see and interact with.
Triangles are supported by all 3D software. This is for instance why you often get triangulated meshes when importing third party 3D models that may have been created in another application. It allows for the best possible compatibility between 3D software.
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Triangles aren't inherently bad, but they can create issues when we use them incorrectly. In general, we should try to avoid them in our meshes.
With that said, triangles can also be the only solution to modeling challenges sometimes. For instance, you may have a topology that ends in an uneven number of vertices. In these cases, it is easy to get into the trap of thinking that only quads is the acceptable solution. But this is simply not true. If a triangle is a quick solution for a tricky modeling problem, by all means, add a triangle.
In short, the general rule is to model with quads but don't be afraid of using an occasional triangle. You can start to break the rules once you have an understanding of how the different components of a mesh works. ngons is another example.
Related content: Blender N-gon guide
Let's look at some of the downsides. Here are some of the issues that we may run into when using triangles in our mesh.
As mentioned above there are so many cases where triangles are the quickest solution.
For example, we may need to occasionally create a whole new loop cut in our model to get the extra vertex we need to create a quad without creating a triangle in another part of our mesh. While this may be doable in some cases, if we have a complex mesh, it may just be better to settle for a triangle instead of adding more loop cuts further increasing the complexity of the mesh.
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We also have to consider what the model is going to be used for. For instance, if we intend to use the 3D model in a game engine that will triangulate our mesh either way, the benefits of using quads over triangles for the final result is not warranted.
Instead, it boils down to shading and that it is easier to work with quad topology rather than a triangulated one since a lot of the modeling tools we use are designed to work with quads.
Next, even if we do intend to use the model in software that will ultimately triangulate it, the shading will be better with a quad topology than with a triangulated one. For instance, if we have to bake a normal map, we may want to have a quad topology simply because it will give us a better bake before we export the model.
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The last downside to tackle is the subdivision surface modifier. When adding it to our mesh it will make it all quad topology. Triangles and all kinds of ngons will be converted.
But it may not be converted in the way we intend or it might result in shading issues.
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Quads in general will work much better in many cases, for example editing a quad based mesh is much easier than a triangle-based mesh. We can better manage loops as well as normals, subdivision surface modifiers also work much better with quad based meshes.
So, we have an idea of why Triangles might not be the best solution when creating a mesh but what do those actually look like in practice?
Let's take a look at an example.
In this example I've used triangles to fill the point at the end of this spike. After adding a subdivision surface modifier to the mesh I get some unwanted ridges around the cone that you can see in the first image. I also cannot add loops to the section that has been filled with triangles.
Let's look at another example.
In this example I've recreated the spike using quads instead, while it may not seem as intuitive to create a round shape using squares the results are actually much rounder as I have more control over how the model is subdivided as well as a more even distribution of faces and a smoother result.
Let's look at a third example.
In this example I've created a cube with a rounded edge, while both models look identical in terms of shape, we can see how the triangles I've used in the first example have subdivided differently and are distributed somewhat unevenly.
While this isn't as much of an issue on a flat surface it will disrupt the poly flow of the mesh and on curved surfaces like the one shown in the spike example this distribution can cause unwanted results.
Blender also gives us an option to quickly find triangles in our mesh.
To show triangles in blender:
This will select all faces that have less than four sides and this is all our triangles. We can now easily see them.
Now that we have an idea of why we may not want triangles in our mesh, we will probably want to get rid of what triangles we can.
In most cases we have different modeling problems that over time we will familiarize ourselves with and learn how to deal with. Over time we will recognize the problems that come up again and again as we model and learn how to deal with them through practice.
The most important thing is to build an underlying topology with the edge flow that supports our intentions.
Let's start with a semi-automatic approach to converting triangles into quad.
To turn Tris to Quads in Blender
If there are still triangles in your mesh that you do not want, you will need to modify your geometry in a manual way. In most cases we can use a combination of tools to achieve this.
Here are the tools that I commonly use to turn triangles into quads.
You can refer to these articles to learn more about these tools.
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Combining these tools in various ways depending on how the topology looks usually solves the problem.
If you've ever exported your models to a game engine or seen a wireframe view in a game, you may notice that all of the meshes use triangles.
The reason for this is that triangles are guaranteed to be a flat surface unlike quads which can have bent surfaces.
In general, having a guaranteed flat surface makes the process of rendering triangles simpler than rendering quads and quicker as well which is why most game engines will just triangulate the meshes.
Since some applications require a model to be triangulated, there are cases where we will need to do this manually. This can also be useful in the case that our model is not triangulated correctly on export.
To triangulate a mesh in Blender
This will convert all of the face on our mesh to triangles regardless of their vertex count.
We can also use the triangulate modifier. This is an object mode tool and we can add it to the modifier stack by following these steps:
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Once the modifier is added to the stack, we can choose from multiple ways Blender will determine the direction a quad will be triangulated using the quad method setting.
We can also apply the modifier and manually change some of the triangulations. We can apply the modifier by selecting it and then press Ctrl + A
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Once the modifier is applied, we can tab back into edit mode and go to vertex select mode by pressing one on the number row. Select two connected vertices, press X and choose dissolve edge.
Next, select the two vertices you want the edge to connect and press J to join them.
While we've talked a lot about triangles and quads you may know that faces can connect more than four vertices. These types of faces are known as N-gons.
N-gons are any face that connects more than four edges. We usually avoid using them for the same reason we avoid using triangles, though N-gons again have their uses but they have odd results with subdivision surface modifiers.
If you want to learn more about them you can read this article.
Related content: Blender N-gon guide
To conclude, there are many cases where we will use triangles and quads to create a model's mesh, in general it is best to avoid using triangles as they can cause issues with the shading, polyflow, modifiers and just in general can make it harder to work with a model.
With that said triangles certainly have their uses and can save us a lot of time that might be spent on trying to find the right solution to achieving an all-quad mesh.
Thanks for your time.