Mio3 UV adds the unwrap operators Blender leaves you to write by hand

An add-on that lives in the UV Image Editor sidebar

Mio3 UV is described as an easy-to-use, user-friendly UV editing support add-on for everyone from beginners to professionals, designed to make UV unwrapping more enjoyable, and it includes features particularly suited for character modelling.

It is a Blender add-on, and the location section says where it lives: UV Image Editor, then Sidebar, then Mio3.

That placement tells you the whole design. This is not a separate application that imports and exports UV layouts. It is a panel of extra operators attached to the view you are already in when you are unwrapping, and it works on your existing selection, in the same way the built-in operators do.

The primary language of the repository is Python, the licence is GPL-3.0, and the repository layout matches a Blender extension rather than a plain script. There is a blender_manifest.toml at the top level, which is the manifest the Blender Extensions platform expects, and the code is split across directories with clear roles: operators/ for the operator implementations, ui/ for the panels, classes/ for the property and operator classes, utils/ for the geometry and UV maths, blend/ for bundled blend data, icons/ and images/ for assets, languages/ for localisation, plus preferences.py, property.py, translation.py, globals.py and an __init__.py at the root.

The homepage is not given in the project metadata, but the README links the documentation site at addon.mio3io.com, with English and Japanese versions of the Mio3 UV documentation.

Seven unwrap operators, each with a specific intent

The unwrap operators are where the character modelling focus shows.

Unwrap unwraps while maintaining the original position, size and angle as much as possible, which is the operation you would otherwise do by hand, adjusting the result after an automatic unwrap so the pieces land roughly where the artist expects.

Straight unwraps so that the selected edge loop becomes a straight line. Normalize normalizes the size and position of selected UVs. Gridify unwraps so that the selected face becomes a rectangle, and the README says it can be used for quadrilateral meshes. Rectify unwraps so that the boundary becomes a rectangle. Projection Unwrap unwraps by projecting from an angle parallel to the normal of the face selected in the 3D view. And Virtual Mirror unwraps as if the mirror modifier is applied, which the README marks as v1.6.

The two rectangle operations are worth separating in your head. Gridify works on a single selected face and produces a rectangle for it, which is the building block for laying out a quad mesh. Rectify works on the whole island and squares up its boundary. For a character, a garment or a piece of clothing, the combination of an unwrap that preserves position and a set of small rectangular adjustments is close to the manual workflow that a lot of artists end up doing.

None of these operators is a general purpose unwrap. They are corrections applied to the result of one, and the add-on is at its best layered on top of what Blender already does.

Layout and arrange, the two lists that do the busy work

The Layout Operators and the Arrange Operators together account for most of what the add-on does, and they cover a lot of ground.

Layout starts with Align, which aligns selected elements to the top, bottom, left, right or XY center position. There is a variant that aligns edge loops only in vertical or horizontal directions, and Align Axis adjusts to be vertical to the X or Y axis. Orient World aligns the angle of the island to the Z axis. Sort sorts islands based on coordinates in 3D space, which is the operation that makes a multi-island layout readable rather than a random scatter. Distribute distributes islands evenly, and the README notes a variant that distributes UVs based on geometry to equalize edge length, marked as v1.3.

Arrange adds the operations that reshape rather than reposition. Relax smooths selected vertices. Stack stacks similar islands. Merge merges nearby UVs in the selection. Circle adjusts to form a clean circle. Offset Boundary expands or shrinks the boundary UVs of the island. Align Seams aligns UV coordinates that share the same 3D vertex but are separated by seams, which is a small but real correctness fix. Stretch aligns the width of islands or UV groups, marked v1.3. Copy and Paste UV Shape copies and pastes the shape while maintaining the original position. Shuffle randomly rearranges island positions, exchanging them when two islands are selected.

And then there are three that are specifically for characters. Unfoldify automatically lays out selected islands based on their spatial relationships in 3D space, which is a way of getting a readable arrangement without hand placing each piece. Average Island Scales adjusts size based on the mesh size in 3D space, so pieces come out proportional. Align Body Parts identifies body parts based on coordinates and aligns orientation and order for an intuitive layout.

Align Body Parts is the clearest statement of who this add-on is for.

Symmetry and selection, in 3D space rather than in UV space

The Symmetry Operators and the Selection Operators share a design idea that is worth stating on its own, because it is the add-on's most useful trick.

Both sets of operators work in 3D space rather than in UV space. Symmetry symmetrizes UVs based on 3D space symmetry, and Snap to Symmetry snaps to the closest symmetrical UV. The selection side has Select One Direction, which selects UVs on one side based on coordinates in 3D space, and Mirror Selection, which selects symmetrical UVs based on coordinates in 3D space.

The reason this matters is that UV space has no notion of left and right, front and back, or the symmetry axis of a character. A mirrored pair of UV shells, which is the normal case for a character, is two islands that may have been unwrapped and placed in any orientation. Working out which UVs correspond to which 3D vertices, and which of them are mirror images, is the tedious part, and doing it in 3D space means the add-on can answer it from the mesh.

The remaining selection operators are more familiar. Similar selects similar islands, Boundary selects island boundaries, there is a variant that selects only vertical or horizontal edges, No Region selects UVs that do not have an area, and Flipped UV Faces selects flipped UVs.

Two mark seams operators sit in their own section rather than among the selections. Mark Seams Angle-Based and Mark Seams on Selection Boundary. The first is the standard angle based approach, and the second marks the boundary of what you have selected.

The utility tools, and two that use Geometry Nodes

The Utils section is four items, and two of them are built on Geometry Nodes rather than on the UV editor.

Original Checker Map uses a cute original checkered map, using Geometry Nodes. Padding Overlay displays a padding overlay. UV to Mesh sets up a modifier for UV to Mesh, also using Geometry Nodes, marked as v1.2. And Exposure Adjustment adjusts the exposure of the texture when the UV mesh is difficult to see, also marked v1.2.

The Geometry Nodes detail is the interesting one. UV to Mesh is a well known need in texturing, where a texture needs to be projected onto a mesh, and implementing that as a Geometry Nodes modifier means it works with any mesh rather than requiring a baked texture. The README does not say whether the add-on sets up the modifier or provides the node group, and it does not say how the Exposure Adjustment is applied, so those are two questions for the documentation page.

The Padding Overlay is the other one worth noting. Padding is the empty space between UV islands, and it is what stops texture bleeding from one island into the next when the texture is packed. Showing an overlay of the padding region makes the packing visible instead of something you infer from a result.

Two versions, because Blender 5 changed the add-on platform

The install section is the part that catches people out, and it is short.

For Blender 5 and later, the listing is the Mio3 UV Ver 2 build on the Blender Extensions platform. For Blender 4, the README says to use Ver 1.5, and the link points at the versions list for v151.

So the add-on is maintained as two lines rather than one, and picking the wrong one is the likely first failure. The Blender Extensions platform is a different distribution channel from dropping a zip into the add-ons folder, and the version numbering is the add-on's own rather than Blender's, which means Ver 1.5 is a 1.x add-on and Ver 2 is a 2.x add-on that supports Blender 5.

For the developer side, the manifest file blender_manifest.toml is the entry point, the code is split into operators, ui, classes, utils and the rest, and the languages/ directory with translation.py suggests the add-on is localised. The README links Japanese and English documentation, and the description itself carries the ja/en marker in the repository description, so the add-on ships with more than one language.

The Credits section says the add-on includes code derived from and adapted from Blender source code, licensed under the GNU General Public License, which is the same licence the add-on itself uses, so that is consistent.

On maintenance, the repository is not archived and the last push was on 2026-08-03, and the repository has no GitHub releases, so the version you install from the Extensions platform is the version you get.

Where Mio3 UV is the wrong choice

Three cases, and they are mostly about expectations.

The first is if your unwrapping is hard surface rather than character work. The add-on says it includes features particularly suited for character modeling, and the three character oriented operators, Unfoldify, Average Island Scales and Align Body Parts, are built on 3D space coordinates of body parts. On a piece of hard surface geometry, where you are laying out a few large planar shells, the built-in operators and a few minutes of work are usually enough, and a panel of thirty extra buttons is noise.

The second is if you expect it to replace an automatic unwrap. The unwrap operators here are corrections and shapes. Unwrap maintaining the original position, size and angle, and Straight, are the kind of operation you run after a projection or a basic unwrap, not instead of one. If your workflow starts from a cube projection and you want a result that packs tightly, this is not the tool for the first step.

The third is the version management, which is a real operational cost rather than a preference. Supporting Blender 4 and Blender 5 from one repository means two release lines, and the operator sets differ between them, since the README marks several operators with the version they appeared in, v1.3 and v1.6 among them. If your studio is on Blender 5 and a tutorial points at a v1.3 operator, the mapping is on you.

One more thing to check before you install: the add-on is licensed under the GNU General Public License, which is fine for personal and internal use and carries obligations if you redistribute a modified version, though a Blender add-on installed from the Extensions platform is not something most people redistribute.

Editorial conclusion

Adopt Mio3 UV if you unwrap a lot of character meshes in Blender and find yourself writing the same island alignment and seam cleanup by hand. Do not adopt it if your work is mostly hard-surface unwrapping that Blender's own operators already handle, and check the version mapping before installing, because the add-on ships as a separate line for Blender 4 and another for Blender 5. Before you install, read the documentation page for the operators you actually need, since the add-on now spans two major Blender generations and the operator sets differ between them.

Frequently asked questions

Official sources

1. Issues
2. License: GPL-3.0
3. mio3io/mio3_uv on GitHub
4. README