UV Mapping: What UVs Are and How to Unwrap a 3D Model

A 3D model is a shape. Its colors come from a flat picture called a texture. The UV map tells the computer which part of that picture goes on which part of the shape. This guide explains how it works, shows the real UV map of one of our models, and walks through the problems you will meet and how to fix them.

By the Bake3D teamUpdated October 8, 202611 min read

Short answer

UV mapping is how a flat image gets wrapped around a 3D model. The model is cut along lines called seams, and the pieces are laid flat in a square. Each flat piece is an island. U and V are the two directions of that square. Good UVs have no stretching, no overlaps you did not mean, and the same amount of texture on every part. AI-made models come with UVs already done.

How we checked this: On 8 October 2026 we opened our sample fox (made with Bake3D) in Blender 4.4, counted its UV islands and seams with a script, measured its texel density, and made every render on this page in Blender. The Blender steps follow the Blender manual. Outside facts come from the official pages linked below.

Think of a chocolate bunny wrapped in foil. Before it was wrapped, the foil was a flat sheet with a picture printed on it. Someone had to plan where each part of the picture would land, so the eyes end up on the face and not on the back. A UV map is that plan for a 3D model.

What a UV map is

A texture is a normal flat image, like a PNG or a JPEG. A 3D model is made of thousands of small triangles. The UV map gives every corner of every triangle a spot on the flat image. When the computer draws the model, it fills each triangle with the part of the image that sits between its three spots.

The flat image is treated as a square that goes from 0 to 1 in both directions. U is the direction across. V is the direction up. The letters are just the next free ones, because X, Y and Z already name the directions in 3D space. A spot at U 0.5, V 0.5 is the center of the texture, whatever its size in pixels.

Here is the real UV map of our sample fox. We made it from one picture with Bake3D’s image to 3D generator. It has 60,000 triangles and one color texture, 2048 by 2048 pixels.

Three panels of the same fox model. Left, the fox covered in a colorful lettered test grid. Middle, the grid laid flat with the fox's 32 UV islands outlined in white. Right, the real orange fox texture with the same outlines, where the face and eyes are easy to spot. — The same UVs shown three ways. A test grid on the model, the same grid laid flat with the 32 islands outlined, and the real 2048 pixel texture. Rendered in Blender from our sample fox on 8 October 2026.

Look at the right panel. You can find the fox’s face, its white chest and its dark legs. They look cut up and spread out, like the pieces of a sewing pattern. That is normal. The picture only has to look right once it is wrapped back onto the model.

Seams, islands and texel density

Three words explain most of UV mapping.

Cut a box along its seams and it lays flat. Here the top and four sides stay joined as one island, and the bottom becomes a second island.

Seams are the edges where the model is cut open. On the flat image, the two sides of a seam end up in different places. That is why a seam can show as a thin line or a jump in the pattern. Good seams hide in places people rarely look, like under the belly, inside the legs or behind the ears.

Islands are the flat pieces you get after cutting. A box can be one island shaped like a cross, or six separate squares. Our fox has 32 islands. Nine of them are tiny, only 2 to 8 triangles each. The 23 big ones cover the body, head, legs, ears and tail. Together, all the islands use 64% of the texture square. The rest is empty space and padding.

Texel density is how many texture pixels land on each part of the surface. A texel is one pixel of a texture. Adobe’s Substance 3D Painter guide defines it as the number of texels in a given surface area of the model. If the head gets half as many pixels per centimetre as the body, the head looks blurry next to it.

We measured our fox. Every one of its 23 big islands gets the same texel density, about 964 pixels per metre of surface at the size the file comes in. So the texture is equally sharp everywhere. That even spread is what you want.

How to see the UVs of a model in Blender

You can check any model’s UVs in a few minutes. These steps work in Blender 4.4, which we used.

Import the model. For a GLB file, use File, Import, glTF 2.0.
Open the UV Editing tab at the top of the window. You now see the 3D view on the right and the UV Editor on the left.
Select the model and press Tab to enter Edit Mode. Press A to select everything.
Pick the texture in the UV Editor. Use the image menu at the top of the UV Editor. The islands now sit on top of the real texture, like the right panel above.
Add a test grid. In the UV Editor, choose Image, New. Set Generated Type to Color Grid and click OK. The Blender manual says this grid can be used to check for stretching or distortion.
Put the grid on the model. In the Shading tab, add an Image Texture node, pick the grid, and plug it into Base Color. Now the model looks like the left panel above.
Turn on stretch colors. In the UV Editor, open the Overlays menu and turn on Display Stretch. Newer Blender versions call it UV Stretch. Blue means little stretching. Red means a lot.

Each square of the test grid should look like a square on the model, and all squares should be about the same size. If they do, the UVs are good.

Why AI-made models come already unwrapped

A model from an AI 3D tool comes with its UVs and its texture made together. The tool builds the shape, cuts it into islands, and fills those islands with the texture. You do not have to unwrap anything to use the model.

That has a few results you should know about:

The islands are shaped by a computer, not a person. They often have wiggly edges and odd shapes, like the ones in our fox. That is fine for showing the model. It is harder for a person who wants to paint the flat image by hand.
The texture only fits these UVs. If you unwrap the model again, the old texture will land in the wrong places. To keep the colors, you have to bake the old texture onto the new UVs. See fix problems below.
Painting works best in 3D. Because the islands are hard to read flat, paint on the model itself with Blender’s Texture Paint mode. The manual notes that the object must first be unwrapped, and an AI model already is.

Here is what you get from Bake3D, checked against our studio’s export options:

GLB holds the mesh, its UVs and the PBR texture maps. Turn on PBR textures when you bake to get roughness, metal and normal maps as well as color.
FBX holds the mesh, its UVs and the base color texture.
OBJ holds the shape in its current pose with UVs, but no textures inside.
Textures only downloads the model’s maps as a zip, free: base color, plus normal, roughness and metallic when the model has them. Put them back on the OBJ in Blender, or paint on them.

If the generated topology is a problem, two options rebuild it with clean four-sided faces. The Game-ready mesh option at bake time asks for about 18,000 four-sided faces at no extra cost. Retopologise rebuilds an existing model with about 15,000 four-sided faces for 20 credits and bakes its texture again onto the new surface. See pricing for the full list.

Want to try it on your own picture? Start on the image to 3D page, or play with finished models first in the free 3D demo.

Common UV problems and how to fix them

We made the three renders below from the same fox. Only the UVs change. The middle one uses UVs projected flat from the front. The right one has the head islands shrunk to 40% of their size.

Three close renders of the fox head and chest covered in a grey checker pattern. Left, small even squares everywhere. Middle, the squares become long stripes on the neck, cheeks and body sides. Right, the squares on the head are much bigger than on the body. — Good UVs, stretching, and uneven texel density, all on the same fox. Only the UV map changes between the three. Rendered in Blender on 8 October 2026.

Stretching

What you see: squares on the test grid turn into long stripes or bent shapes. A face texture looks smeared.

Why: an island was flattened in a way that pulls some triangles longer than they are on the model. Flat projections cause this on every surface that faces sideways, like the middle fox.

Fix: add a seam where the stretch is worst, then unwrap again. In Edit Mode, select the edges, then use Edge, Mark Seam. Press U and pick Unwrap. The Blender manual says the angle based method gives a good flat version of a mesh, and the conformal method works better on simple objects.

Uneven texel density

What you see: some parts look sharp and others look blurry or blocky. The test grid squares are bigger on one part, like the right fox’s head.

Why: the islands were scaled differently, so some got more pixels than others.

Fix: select all islands in the UV Editor and use UV, Average Islands Scale. It scales the islands so they are all about the same scale. Then use UV, Pack Islands to fit them back into the square. If one part matters more, like a face, you can then make its island a little bigger on purpose.

Overlapping islands

What you see: paint you add in one place also shows up somewhere else.

Why: two islands sit on top of each other, so they share the same pixels.

Fix: use UV, Pack Islands. It moves and turns the islands so none of them touch. Overlaps are not always wrong, though. Artists overlap the left and right halves of a symmetric model on purpose to save space. But maps for baked lighting must never overlap. Unity’s manual says lightmap UVs should not have any overlapping faces.

Lines at the seams

What you see: a thin dark or bright line along a seam, often when the model is far away.

Why: games use smaller copies of a texture, called mipmaps, for far objects. When the texture shrinks, color from just outside an island leaks in. Adobe’s guide says padding is important for mipmaps because it stops wrong colors from bleeding into the UVs.

Fix: leave a margin between islands when you pack them. Bake or export the texture with padding, so the color around each island is filled with the island’s own edge color. You can see that padding in our fox texture as the blocky color around each island.

Mirrored or upside down text

What you see: a logo or text reads backwards.

Why: the island is flipped in the UV square.

Fix: select the island in the UV Editor and mirror it, then check the logo again on the model.

Unwrapping a model yourself

If you modeled something by hand, or you need new UVs, these are the main tools in Blender’s UV menu. Press U in Edit Mode to open it.

Tool	What it does	Good for
Unwrap	Flattens along the seams you marked	Characters and anything you care about
Smart UV Project	Cuts the model by itself wherever the surface bends sharply	Quick results on hard objects like crates and robots
Lightmap Pack	Gives every face its own space	Baked lighting, not hand painting
Pack Islands	Moves, turns and scales islands to fill the square with a margin	The last step after any unwrap

The Blender manual warns that Lightmap Pack usually makes a broken up, distorted map that is a poor fit for texture painting. Use it only for lighting.

Keep the colors when you re-unwrap an AI model

New UVs make the old texture land in the wrong places. Bake it across instead:

Duplicate the model. Keep the original as it is.
Unwrap the copy with new seams, then pack the islands.
Add a new blank image to the copy’s material, in an Image Texture node that is not connected to anything. Keep that node selected.
Select the original, then the copy, so the copy is active.
Bake in Cycles with Bake Type set to Diffuse, only Color turned on, and Selected to Active turned on. The manual describes it as baking from the selected objects to the active one.
Save the new image. The copy now has clean UVs and the same colors.

Baking also needs a UV map on the copy, so unwrap before you bake.

UV rules in game engines and file formats

glTF and GLB store UVs as TEXCOORD_0, with more sets allowed. The glTF spec says texture coordinate 0, 0 is the top left corner of the image. Blender shows 0, 0 at the bottom left. Importers handle this for you, so only think about it if you write your own tools.
Roblox asks for a single UV set, all inside the 0 to 1 square, and allows overlapping UVs. Our Roblox guide covers its other limits.
Unity and Unreal Engine use a second UV set for baked lighting, and that one must not overlap.

If you also need fewer triangles, do that before you unwrap again, or check the texture after. Our guide on reducing polygon count explains how the Decimate modifier treats UVs. To learn what a GLB file holds besides UVs, read what is a GLB file.

Questions people ask

Why is it called UV mapping?

X, Y and Z are already used for the three directions in 3D space. So the two directions of the flat texture square got the next free letters, U for across and V for up.

What is the difference between UV mapping and UV unwrapping?

Unwrapping is the step where you cut the model and lay it flat. The UV map is the result, the saved list of where every corner of the model sits on the texture.

Do I need to UV unwrap a model made with AI?

Usually not. AI 3D tools give you a model with UVs and a texture that already fits them. Unwrap again only if you need cleaner islands for hand painting, a lightmap, or a game rule the current UVs break.

Can a model have more than one UV map?

Yes. glTF files can hold several sets, and games often keep a second one for lightmaps. Some platforms take only one. Roblox, for example, asks for a single UV set inside the 0 to 1 square.

What does texel density mean?

It is how many texture pixels cover one piece of the model's surface, for example pixels per metre. When every part has about the same density, the texture looks equally sharp everywhere.

Why does my texture look blurry or have lines at the seams?

Blur usually means the island is too small for its size on the model, so it gets few pixels. Thin lines at seams usually mean too little padding around the islands, so color from outside an island leaks in when the texture is shrunk.

Sources

About this guide

Written and kept up to date by the Bake3D team. We build a tool that turns one image into a textured, rigged and animated 3D model, and we test the steps in our guides on our own files. First published October 8, 2026. See how we write and check guides, or send a correction to hello@bake3d.ai.

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