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What is a UV map? How UV maps and island selection work

Why the paint lives on a flat sheet, why that sheet looks like a messy puzzle, and how island selection saves you.

Explainer

6 min read

Updated

Basics

A UV map is the guide that connects a 3D outfit to the flat picture it is painted on. Every outfit in the game is a 3D shape, but the paint on it lives on a flat picture, like the skin you swap onto a character. This article explains how the two connect, and why the flat picture looks so strange.

The big idea: a flat sheet wrapped around a 3D shape

The flat sheet gets wrapped around the 3D jacket
The flat sheet gets wrapped around the 3D jacket

Two everyday things work the same way. Pick the one that clicks for you.

The Earth is a ball, but a map is a flat picture that gets wrapped around it. That flat map is the "UV map" of the planet.

A flat world map wrapped around a globe, the same idea as the flat sheet and the jacket
A flat world map wrapped around a globe, the same idea as the flat sheet and the jacket

Why does the sheet look so weird?

A UV sheet looks like a messy puzzle, and that is normal: it is not broken. The pieces were cut to fit around a 3D body: curvy, stretched and sometimes upside down, since they only need to make sense once they're wrapped back on the outfit.

Sleeves
Look like flat tubes.
Chest
Looks like a bent rectangle.
Some pieces
Are mirrored or upside down to save space.
The same idea, with the pieces labeled: front, back, sleeves, collar and cuffs
The same idea, with the pieces labeled: front, back, sleeves, collar and cuffs

Weird on the sheet, perfect on the model.

Why is it packed like Tetris?

UV pieces are packed tightly on purpose. Every pixel of the sheet costs memory and power, and the game has to load it for every player on screen. So creators stack the pieces as tightly as they can, with no big empty gaps, to fit more detail into a smaller image.

Faster loading
A smaller sheet is less to download for every player on screen.
Smoother FPS
Less memory and power spent on every frame.
Sharper paint
The same sheet size gives more detail where it counts.
Left: wasted space (red). Right: the same pieces packed tight like Tetris
Left: wasted space (red). Right: the same pieces packed tight like Tetris

Duplicated regions

Sometimes one region of the sheet is used on two or more parts of the 3D object. A left and a right sleeve, for example, can share the same patch of the sheet, so whatever you paint there shows up on both. It saves space.

One sleeve island on the sheet is used by both sleeves, so the patch shows up on each
One sleeve island on the sheet is used by both sleeves, so the patch shows up on each

Island selection

In our studio

Island selection

U

Island selection picks one whole piece of the UV sheet in a click. Each piece of the unfolded sheet is an island, a patch that floats on its own. Many islands are semantic: they belong to an identifiable part of the 3D object, like a sleeve on a jacket, so the studio lets you select by region.

Click the left sleeve and only the left sleeve is selected, so you can fill it with a color or a pattern without touching anything else. No careful tracing and no painting outside the lines.

Click a sleeve and its whole island is selected, on the sheet and on the jacket, ready to paint
Click a sleeve and its whole island is selected, on the sheet and on the jacket, ready to paint

What to remember

Tick each one when it clicks.

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