Blender
UV unwrapping
So you've sculpted a model. It looks great in Blender. But when you try to add a texture or paint it, the colors just smear across the surface wrong — like someone wrapped a sticker around it blindfolded.
That's where UV unwrapping comes in.
UV unwrapping is the process of taking a 3D model and flattening its surface onto a 2D plane, like peeling an orange and laying the peel flat. The "U" and "V" are just the names for the 2D coordinates (like X and Y, but for texture space).
Without a UV map, Blender (and Three.js) doesn't know how to map your 2D texture onto the 3D surface. With one, you can paint faces, add decals, or apply photorealistic materials.
the metaphor that makes it click
Think about a gift box:
- The box is your 3D model
- The wrapping paper is your texture
- The way you fold and cut the paper to cover the box perfectly — that's the UV map
If you just mash the paper onto the box, you get wrinkles and tears. But if you cut the paper into panels that match each side of the box, you get a crisp, clean wrap.
That's UV unwrapping — deciding where to "cut" the 3D surface so it can lie flat.
marking seams — the most important part
A seam is a cut in your mesh that tells Blender "split the mesh here so it can flatten out." Finding good seams is the entire art of UV unwrapping.
where to put seams
The golden rule: hide your seams where nobody will see them.
Good seam locations:
| Object | Where to put seams |
|---|---|
| A character head | Behind the ears, under the chin, back of neck |
| A human body | Inside the arms, down the spine, inner thighs |
| A cube / crate | Along the hidden edges (back-bottom corner) |
| A cylinder / arm | In a straight line down the back |
| A tree | Up one side of the trunk, along branches |
how to mark a seam
- Switch to Edit Mode (press Tab)
- Select Edge Select mode (the little edge icon in the top-left, or press 2)
- Hold Alt and click an edge loop to select a ring of connected edges (or Shift + Alt + click for multiple loops)
- Right-click → Mark Seam (or Ctrl + E → Mark Seam)
The edges will turn red — that's your seam. To remove a seam: select the edge, right-click → Clear Seam.
Pro tip: Put your seams on flat surfaces or sharp corners — they're much easier to hide than seams running across a smooth face.
the actual unwrap
Once your seams are marked, the real work is one button press:
- Stay in Edit Mode
- Select all faces (A)
- Press U → Unwrap
- A 2D version of your model appears in the UV Editor (the bottom-left panel by default, or split your viewport)
If it looks like a tangled mess — your seams are wrong. Clear them (Ctrl + E → Clear Seam), try a different layout, and unwrap again.
what a good unwrap looks like
In the UV Editor, you want:
- No overlapping islands — each face should sit separately (unless it's a symmetrical part you want to share the same texture space)
- Reasonably straight — islands shouldn't look like crumpled paper
- Good use of space — islands should fill the 0–1 square efficiently, not all squished in a corner
- Consistent scale — faces should be roughly the same size in UV space (so your texture doesn't stretch on some faces and compress on others)
checking for stretching
Blender shows you how bad your UV map is with real-time feedback:
- In the 3D viewport, turn on Display → Viewport Overlays (the little overlapping circles icon in the top-right)
- Enable UV Stretch → Area or Angle
The model will show a heat map:
| Color | Meaning |
|---|---|
| Blue | No stretching — perfect UVs |
| Green | Minor stretching — probably fine |
| Red | Major stretching — your texture will look warped |
If you see red, you need better seams, or you need to use a different unwrapping method.
the different unwrap methods
Press U in Edit Mode and you'll see a ton of options. Here are the ones worth knowing:
| Method | When to use |
|---|---|
| Smart UV Project | Automatic mode for hard-surface objects — great for buildings, props, anything with flat faces |
| Unwrap | The manual one — uses your seams. Best for organic models |
| Project from View | Takes a snapshot from your current camera angle — great for decals and face-projection texturing |
| Cube / Sphere / Cylinder | Wraps the mesh in a simple shape — handy for quick-and-dirty maps on basic primitives |
| Follow Active Quads | Perfect for UVs on quads — makes clean, rectangular islands for things like walls or screens |
Smart UV Project is the cheat code for hard-surface models. It automatically finds seams along sharp edges and lays out the islands. Try it first on any mechanical or architectural object:
U → Smart UV Project → set Angle Limit to 66° (default is fine)