3D Topics - Introduction to "Topology"
How Faces, Edges, and Vertices Connect in a Model
What is Topology?
Topology is the structure of how the faces, edges, and vertices connect on a given model.
Every model has its own topology.
Whether conscious of it or not the artist is always creating and manipulating topology when
they create or edit any model.
The Fundamental Elements
As stated, all topology technically boils down to three basic parts: Faces, Edges, and Vertices.
Vertex - A singular point on a 3D model, by which two or more edges connect to.
Edge - A line connecting two vertices together in a 3D model.
Face - The flat plane created by the intersection of connected edges and vertices.
This is often a square or rectangle shape, but can be other shapes as well.
Triangles, Quads, and N-Gons
Depending on the arrangement of these basic concepts (faces, edges, and vertices), some topology is "better" or "cleaner" than others.
"Clean" topology is generally easier to work with, better to animate with, and generally just universally preferred.
So at this point, you might be asking "okay but what makes 'good' topology?"
The answer to this gets really complicated, really fast.
To start, we can have different "shapes" for our faces.
These shapes are mostly determined by the number of edges/vertices that make up a given face.
Quads - A "quad" is a face made of exactly 4 vertices and 4 edges.
Quads are "the golden standard", and in most situations, we want as many faces as possible
to be quad shaped, particularly when starting out.
A quad doesn't have to come in the shape of a square or rectangle, it can be all sorts of shapes, as long as there are 4 edges and 4 vertices.
As we develop our skills and learn more, we'll find some situations where we can get away with triangles. But for simplicity for now, try to always create quads when possible.
Triangles - A "triangle" is a face made of exactly 3 vertices and 3 edges.
This is the smallest possible face.
Triangles aren't as universally ideal as quads, because it tends to be harder for artists to safely manipulate them.
However, technically most software converts all topology to triangles behind the scenes. So if used properly, triangles won't necessarily break anything. It's still generally better to use quads when possible though.
N-Gons - N-gons are any face that has 5 or more edges and vertices.
Unlike triangles or quads, n-gons don't have a consistent shape.
That's because a face with 5 edges will generally look very different than a face with 6 edges,
or one with 9 edges.
As a general rule, particularly when starting off, it's best to try to avoid n-gons whenever we can.
N-gons tend to be problematic due to a few reasons:
Many n-gons make it harder for artists to understand the model.
Even a single n-gon can significantly break model edge flow.
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N-gons (as well as triangles, sometimes) will create visible artifacts and issues when deforming the model.
It's generally just harder to edit a model that has n-gons.
An Analogy
If all of that seems difficult to remember, we can make an analogy to the weather.
Think of Quads like a bright, sunny day.
Everything is good.
We can go on picnics or go to the beach.
Pretty much everyone is happy.
Yay!
Then we can think of Triangles as a cloudy day.
It's a little bit less bright, a little bit less nice.
But it's still manageable, and we can live with it.
In this analogy, if quads resemble a sunny day and triangles resemble a cloudy day...
Then an n-gon is "a tornado just tore through our neighborhood, the last thing on our mind is going to the beach."
