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Mesh Structure, Supportive Edges & Edge Flow

Basics of topology in 3D modeling

I understand we all wanna create cool robots. But before making robots, let´s
talk a bit about basic topology principles.

I would also like to give a quick thanks to everyone who joined our Discord.
Your questions really helped shape this post.

Alright, jumping into the topic. How to understand topology in 3D modeling?

When we talk about the topology in 3D, we are referring to edge distribution
throughout the model. To demonstrate an example, have you ever asked
yourself any of the following questions?

How do I know that my edges have proper ow?

How do I know if I have even distribution of edges in my mesh?
How do I know if my mesh is clean?
How do I know if there is pinching? 󰊐
Why does my subdivided mesh look so deformed?

All of these questions are based on topology, e.g. how edges are organized
on any given model.

But are there rules or a work ow that is easy enough to understand, so we

can apply it every time we approach a new project?
Well yes… and no. There are very easy rules to remember,  but learning to
apply these rules properly to di erent meshes, will require a lot of practice.

Where to begin?

So what is the proper topology in 3D modeling?

Let me rst show you a few examples where topology became problematic,
and then let´s see if we can nd an easy solution to the problem.

In this example, we can see that there is some distortion on the mesh. But we
already know, the closer two edges are to one another, the sharper the area.

So why is this happening?

We can clearly see that corners in the yellow highlighted area are forming a
sharper corner right?

While it is true that two close edges will give a sharper corner, there might be
some deformation if those same edges are super close on one end, and
widely spread on the other.

Like we see in an example above, a wide edge spread area on the left, is
gradually owing into a narrow edge spread area on the right (highlighted
yellow). The transition between these two areas of the mesh, where we have
a big empty area with no edges will cause deformation. There is simply not
enough geometry there to support that structure.

In order to avoid the problem, we would need more edges to release some of
that tension.
So what would be the easiest x for this problem?
The answer is, create more of an even edge spread (or edge distribution).
While adding new edges, we need to be sure that our edge spread is even
and looking like squares. Also known as quads.

Much better! Ok, so now we know we need an even spread of edges to avoid
distortion. But even spread alone is not enough. If the spread number (or poly
count) is too low, we might encounter the same issue later when we need
more geometry for details. So what do we need to avoid this type of
distortion?

We need even edge distribution that is not too dense or not too
widespread.

There are positive and negative sides to manipulating edges in both low and
high poly (edge) count. Let´s see what they are.

Low poly count

The positive: Low poly count will enable us to easily modify the shape and
block the idea out.
The negative: We can not establish details with a low poly count. The more
details we want, the more geometry we will need.

High poly count

The positive: With larger polycount, we easily can add more details, and
easily tighten the mesh.
The negative: On the other hand, larger polycount meshes are harder to
control because there are more points and edges to manipulate.

Rules to follow so far

So, if we summarize this information, what would be a conclusion or the rule

we would apply to our work ow?

1. We need to start very low poly.

Why? Because the mesh is easier to control and helps us establish our
shape faster.

2. We need to make sure to have even edge distribution.

Why? Because we want to be sure we have enough geometry for our details
and sharp corners. Uneven edge spread can lead to unwanted results as we
´ve seen in our rst example.

Great! Two simple rules to begin with. Not so hard to remember right? But is
that all?
Nope… we have two more. If we now check our progress, what would be our
next step? Our last example shows that geometry has no distortions due to
evenly spread edges, but now the corners are no longer sharp.
In order to do that properly, we need to get ourselves familiar with supportive
edges and edge ow. Let´s do that next.

Supportive Edges

What is a supportive edge?

Supportive edge will simply make sure that your object maintains sharpness
once the subdivision is applied.
Any edge/shape we wish to tighten will need at least one or two
(recommended) supportive edges. Usually, that is the outline of our model.
Two edges close together will form a sharp corner. We just need to follow this
rule.

So in our example, where would we position our supportive edge?  We

previously mentioned the outline, right?
If that is the case we can either extrude the outline edges (shown yellow)
outside or duplicate the edge on the inside. And that is how we set a
supportive edge.

Once the shape is extruded, the outline edge should ideally be surrounded by
2 supportive edges.

Now we can quickly check how our mesh would look like if we apply
subdivision. It looks ok, and it appears there is no distortion on the surface
once we bend it. Good enough so far.

Let’s add supportive edges to our rules list as well.

Rules to follow so far

1. We need to start very low poly.

Why? Because the mesh is easier to control and helps us establish our
shape faster.

2. We need to make sure to have even edge distribution.

Why? Because we want to be sure we have enough geometry for our details
and sharp corners. Uneven edge spread can lead to unwanted results as we
´ve seen in our rst example.

3. We need to add supportive edges.

Why? Because supportive edges will make sure our main shape (or outline)
keeps its structure once we apply subdivision.

Edge Flow

What is edge ow, and what is edge redirection?

In many situations, our rst three steps will not always give us the result we
want. Some corners might not be as sharp or soft as we want them.

In our case, all of the corners are still very soft, instead of sharp and crisp.

Now we need a way to manipulate the topology we already have to get results
we want, right? But not just that, we also need to keep our topology clean
while maintaining quads.

If this area sounds a bit confusing, it just takes practice. More examples you
go through, more it will become clear.

Let´s talk redirection rst. We can start from our supportive edges, as they
provide enough geometry to form a sharp corner.

If we go back to the very basics, we would have two examples. One example
will have a soft corner and the other will have more shaper corner. Notice the
di erence?

So based on the example above, let´s go ahead and apply sharp corners
using supportive edges where we can.

Now we are slowly closing into our nal shape, and as you can notice there
are only two more corners to sharpen.

Here is what we´re going to do. We need to rearrange our edges in a way so
that they have a “gravity ow”. Say whaaaaat??

Yeah, its a thing that helped me understand this edges thing a bit better so
hopefully, it will help someone else as well.

In the example below, we can see our current edge ow on the left. But now
let´s check example in the middle.

We have a gray outline which represents our supportive edge. Now let´s also
pretend that there is gravity force there, and depending on which angle we
would walk on, that would be the ow for the edge (shown yellow). We just
need to apply this logic to rearrange the edges, so they work in favor of the
shape.

In the example on the right, I now removed the edges that we do not need, so
we have more room to follow the “gravity” of our shape.

Ok, our original mesh is positioned left. Then, as shown in the middle, we
would remove edges we do not need and organize the ow of the ones that
do not match the “gravity” ow. Then, as shown in the example on the right,
we would bring back the edges to the mid areas, to make all edges more or
less evenly spread out once more.

This would be it guys! There are multiple other variations on how you could
tackle this, but I tried to keep it straight simple and to the point.

Let´s just break down the rules one more time now that we are done.

Rules to follow on topology in 3D modeling

1. We need to start very low poly.

Why? Because the mesh is easier to control and helps us establish our
shape faster.

2. We need to make sure to have even edge distribution.

Why? Because we want to be sure we have enough geometry for our details
and sharp corners. Uneven edge spread can lead to unwanted results as we
´ve seen in our rst example.

3. We need to add supportive edges.

Why? Because supportive edges will make sure our main shape (or outline)
keeps its structure once we apply subdivision.

4. We need to check if our edge ow is correct.

Why? Because di erent edge ows will give di erent results on the
subdivision. This part will take practice.

NOTE: While these can be simple rules to follow, some factors may vary. For
example, supportive edges can be added later, after you manage your edge
ow. But it is a good practice to get to know the rules rst, later the same rules
can easily be broken and manipulated to match your work style.

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11 Comments

andres
 August 18, 2020 at 6:52 am

Interesante, me hubiera gustado ver esto en español, apenas entendí con mi idioma en castellano
acostumbrado, interesante los tutoriale pero no se bien el ingles, haber si te animas y haces una vercion en
castellano pues………… como los de unreal latam………………..si lo compro

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Kento Kamei
 April 2, 2020 at 10:03 am

Thank you for explaining these rules!

These rules made my understanding of edge ow and topology!

Cheers!

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Anonymous
 March 2, 2020 at 8:40 am

Jest Pan wielki, a właśnie mam problem nie mogę przypisać środkowego klawisza myszy do piórka tabletu
staram się coś skleić w Maya może spotkał się Pan z takim problemem? tablet wacom jeśli ta wiedza
mogłaby pomóc.Pozdrawiam

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Asadullah Sanusi
 January 8, 2020 at 12:38 am

Thank you very much for explaining this to us

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Matt
 December 23, 2019 at 9:59 am

Man, thank you so much for sharing this. It clari ed a lot to me. Cheers.

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Bha
 November 29, 2019 at 6:11 pm

Three things: I’ve kinda developed a man-crush on your modeling expertise – you rock! I am writing this, not
really to share all of the many positive comments I have for you, your skill, care and patience, which I have
an abundance of, rather, I have spent three days, 60+ hours hours trying to model a fairly simplistic object
and I am literally, no further than the starting block – for the Nth time. Grrrr. regardless, the reason for writing
this this time, is your preface to this speci c series whereby you indicate it DOESN’T matter what app we
are using, Maya, C4D, etc…except it DOES matter UNLESS, you can show me where to nd ‘o set’ and
add thickness with caps ON in c4d. You see, no o set, and when I select the outer edge loop and then
‘extrude’ it will extrude, but without caps. so trying to follow along is, in fact, impossible, rendering anything
that follows merely TV (passive entertainment) version instruction (active build knowledge). If this sounds a
little vent’y, sorry, not my real intent, perhaps I should sleep, but I am not upside down on this crucial, but
basic shape and am bummed.

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Mario
 November 30, 2019 at 8:08 am

Hey, thanks for your input. The software truly does not matter as these principles are same in Maya or
C4D. To add caps to extrude in C4D just select Create Caps in the options menu. I have older videos
on Intro to basic C4D tools so maybe check those out too.
Cheers!

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Gamal Emira
 November 22, 2019 at 11:46 pm

Hi, I noticed that the Pen image in your tutorial more clearer than the image I did download. Do you have a
sitting in maya that made it like that? Thanks

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Mario
 November 24, 2019 at 9:53 am

No, but you can just google Wacom pen until you nd one with high enough resolution. That is what I
did.

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frankie.shin
 October 3, 2019 at 10:34 am

Thanks for the great topology explain!

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Nathan Beguin
 September 23, 2019 at 10:04 pm

Being looking for a thorough explanation of bare 3D modelling fundamentals everywhere and nally found
it. There should be more explanations like this. Thanks a lot!

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