【Blender】Complete Guide to UV Mapping - Properly Placing Textures

Overview

To apply textures (images) to a 3D model, you need to perform "UV mapping." UV mapping is the process of unfolding a 3D shape into 2D and defining which part of the texture corresponds to which part of the model. This article covers everything from UV mapping basics to practical techniques.

What is UV Mapping?

"UV" refers to coordinates on the texture image (U and V are used because X, Y, and Z are already used for 3D space coordinates).

Think of it like:

• 3D model = Gift box
• UV mapping = Blueprint for wrapping the box
• Texture = Wrapping paper design

Poor UV mapping causes textures to stretch, distort, or appear in unintended positions.

Opening the UV Editor

1. Select the "UV Editing" workspace at the top
2. Or in any area, "Editor Type" → "UV Editor"

The UV Editor appears on the left, 3D viewport on the right.

What are Seams?

Seams are the "cut lines" for unfolding a 3D model into 2D.

Think of it like deciding where to cut when flattening a cardboard box.

Creating Seams

1. Enter Edit Mode (Tab)
2. Switch to Edge Select mode (2)
3. Select the edges to cut
4. Ctrl + E → "Mark Seam"

Seam edges display in red.

How to UV Unwrap

After setting seams, unwrap the UVs.

Basic Unwrap

1. In Edit Mode, select all (A)
2. Press U → "Unwrap"

The unwrapped UV map appears in the UV Editor.

Types of Unwrap

Method	Description	Best For
Unwrap	Unfolds according to seams	Organic shapes, characters
Smart UV Project	Automatically determines seams	Buildings, mechanical objects
Cube Projection	Projects from 6 directions	Cube-like shapes
Cylinder Projection	Projects cylindrically	Pipes, bottles
Sphere Projection	Projects spherically	Planets, balls

Smart UV Project

A method to automatically unwrap UVs without setting seams.

1. In Edit Mode, select all (A)
2. Press U → "Smart UV Project"
3. Adjust angle threshold (default 66°)

• Advantage: Creates UVs quickly
• Disadvantage: Not as clean as manual unwrap

Editing UVs

You can edit UV islands (unwrapped parts) in the UV Editor.

Basic Operations

• G: Move
• R: Rotate
• S: Scale
• L: Select island

Useful Functions

Operation	Shortcut	Description
Align UVs	Shift + W	Align UVs along an axis
Pack UVs	Ctrl + P	Efficiently arrange UV islands
Average Scale	Ctrl + A	Unify island sizes

Checking Textures

Methods to verify UV mapping is correct.

Using a Checker Texture

1. Open Shader Editor
2. "Add" → "Texture" → "Image Texture"
3. "New" to generate a checker pattern
4. Connect color output to Principled BSDF Base Color

If the checker pattern isn't distorted, UV mapping succeeded.

Common Problems and Solutions

Texture is Stretched

• Cause: UV island proportions don't match the original mesh
• Solution: Adjust the affected area in UV Editor, or re-unwrap

Texture is Flipped

• Cause: Face normals may be inverted
• Solution: Select faces in 3D view → Alt + N → "Flip"

Seams are Visible

• Cause: Seam placement is in a noticeable location
• Solution: Move seams to less visible areas (back side, natural folds, etc.)

UVs are Overlapping

• Cause: Multiple UV islands are in the same position
• Solution: Ctrl + P to pack UVs, or manually move islands

Tips for Efficient UV Mapping

1. Minimize seams: Too many creates more visible seams
2. Place seams in hidden areas: For characters, use armpits, clothing seams, etc.
3. Consider texture resolution: Make important areas larger in UV space
4. Ensure padding: Leave space between islands to prevent bleeding

Summary

• UV Mapping: Unfolds 3D models into 2D to define texture coordinates
• Seams: Specify where to cut for unfolding
• Unwrap: Generates UVs according to seams
• Smart UV Project: Creates UVs quickly and automatically

UV mapping may feel difficult at first, but the intuition develops with practice.