3D Topics - Edge Flow

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Edge Flow

Edge Flow is the routing of edge loops around a model, depending on the presence (or lack of) N-Poles, E-Poles, and layout of general topology in a mesh.

Edge flow is important because it can directly affect both the appearance of a model (particularly when using subdivision to model) and affect how a model deforms (such as when animating the model).

Core Components of Edge Flow

At the simplest for, edge flow is primarily influenced by poles.

When an e-pole or n-pole is present, they inherently change the direction of edge flow. The way the direction changes depends on what pole type is used.

In the below examples:

The red circle indicates the pole.
The red lines indicate the edges that converge to create the pole.
The blue dotted lines indicate the direction the edge flow changes.

Example of how an n-pole (3 incoming edges) affects edge flow.

Reminder that an n-pole is a pole with 3 incoming edges.

In such a case, this shape tends to bend edge flow inward curving it towards the pole.

Examle of how an e-pole (5 incoming edges) affects edge flow.

Reminder that an e-pole is a pole with 5 incoming edges.

In such a case, this shape tends to bend edge flow inward curving it towards the pole.

The direction of flow matters because, as stated above, it can affect the appearance of a model, as well as how it deforms such as when animating.

In general, an "ideal" model will use edge flow to keep edge loops localized, and to avoid having crazy loops that travel in all sorts of directions, all around the model.

Just like edge loops, edge flow can be examined by taking out the "loop cut" tool (or equivalent for the software) and then examining how the loop travels through the model. If there are any edges that take unexpected, crazy twists and turns as it goes all around the model, then there might be improvements to be made with edge flow.

External References

Relevant Youtube Videos

Youtube | You Should Use All Quads When Subdivision Surface Modeling - Blender Beginner Tutorial

By CG Cookie

Examples of how quads and edge flow matter on a more advanced model.

Youtube | Importance of Edge Flow in 3D Modeling (Control the Forms)

By Mario Elementza

Good visual examples of how to manipulate edge loops and edge flow to change how a model looks.

Youtube | Clearly Define Details with Loops when 3D Modeling - Blender Beginner Tutorial

By CG Cookie

Clear visualizations of using edge loops and edge flow to define model details.

Youtube | The Importance Of Good Edge Flow _ Blender Topology Tutorial _ #19

By CRNT DESIGNERS

Demo of using Blender to combine some basic shapes, while creating good edge flow.