UV RectiPack

Select your faces and press Straighten & Pack.UV RectiPack unwraps the mesh if needed and turns wobbly quad islands into straight grids. It cuts over-long strips, stacks duplicates,shrinks faces nobody can see, and packs everything at the largest uniform texel density that fits, with margins that survivemipmapping. One UV Check then tells you PASS or FAIL, and Fix All repairs what it can.

Full docs with videos for every feature: dawczens.github.io/uvrectipack.github.io/

Installation

1. Download uv_rectipack-1.0.0.zip. Don't unzip it.
2. In Blender open Edit → Preferences → Get Extensions, click the ▾ menu at the top right and choose Install from Disk…
3. Select the zip. The add-on is enabled at once, with no restart.
4. In Edit Mode press N in the UV Editor or the 3D Viewport and open the RectiPack tab, or press Shift+Alt+U for the pie menu.
5. To update, install the new zip the same way. To remove it, go to Preferences → Add-ons → UV RectiPack → ▾ → Uninstall.

⚡ Straighten & Pack - the one-click workflow

The main button does everything in order. It unwraps the mesh if it has no UVs, straightens grid islands, cuts over-long strips, stacks duplicates if enabled, and packs at the largest texel density that fits. A report then shows coverage and density before → after.

Kitbash crate: 72 islands, one click

How to use

1. Select one or more mesh objects and press Tab to enter Edit Mode.
2. Press A to select all faces, or select only the part you want to process.
3. Open the sidebar with N and go to the RectiPack tab, in the UV Editor or the 3D Viewport. Or press Shift+Alt+U for the pie menu.
4. Choose a preset and the texture size, then click Straighten & Pack.
5. Read the report box, e.g. Coverage 59% → 87% · TD 443 → 539 px/m (+22%). Change any option in Blender's Adjust Last Operation panel (F9) and the result updates live.

▦ Straighten islands

Quad islands become clean, axis-aligned grids, so textures, trims and tiling patterns run straight.

Bent pipe and wrap strap become straight grids

Spiral strap: one long strip is cut into segments that pack tightly

How to use

1. Select the faces. To change the shape only, click Straighten in the Straighten panel; packing is a separate step.
2. Pick a mode: Proportional keeps the real 3D edge lengths, Even Grid makes all columns and all rows equal, Square makes every quad the same square.
3. Leave Partial Grids on. Islands with a few triangles, n-gons or poles get their quad region straightened and the rest relaxed around it.
4. Leave Split Long Strips on for square textures. A strip longer than half the texture is cut along grid lines into equal segments.
5. Click Orient to rotate any island to its tightest bounding box without reshaping it.

⬒ Pack at maximum texel density

Islands are scaled to their true 3D size, so every island gets the same px/m. A multi-strategy rectangle packer then searches for the largest scale that fits. In our tests it gained 10-20% texel density over Blender's built-in packer at the same pixel margin.

Presets change the margin and alignment; the report shows the gain

How to use

1. Select the islands and click Pack Max Density, or use Straighten & Pack.
2. Pick a preset. The info line shows what it means, e.g. Margin 8 px · mips to 512 px · 4 px blocks.
3. With Separate per Material on, each material gets its own 0-1 space, i.e. its own texture set.
4. Use Min Island (px) to enlarge tiny islands that would otherwise vanish in the texture.

⧉ Stack duplicates

Identical islands, such as bolts, panels and symmetric halves, are packed once and laid exactly on top of each other. The space they free goes to everything else.

10 bolts: 120 islands collapse to 7 placements

Mirrored halves stack too

How to use

1. In the Pack panel tick Stack Duplicates.
2. Keep Mirrored on to also stack mirror-image copies. Turn it off for unique details such as text or decals.
3. Click Straighten & Pack or Pack Max Density. The report shows how many islands were stacked.
4. To stack without packing, click the stack icon next to Pack Max Density.

◐ Smart Priority

RectiPack casts rays from every face to find what nobody can see: contact areas, interiors and undersides resting on the ground. Those faces get a fraction of the density, and the visible ones get more.

Select Hidden Faces previews what will shrink

Stacked crates: contact faces shrink, visible faces grow

How to use

1. Open the Smart Priority panel and click Select Hidden Faces to preview. X-ray (Alt+Z) helps.
2. Tick Shrink Hidden Faces and pack. Hidden faces get Hidden TD × the base density (default 0.25).
3. Want more pixels somewhere? Select faces and click Hero ×2. For less, click Low ×½. Clear removes the marks.
4. Tick Other Objects Occlude when other visible objects, such as a floor, should hide faces too.

✔ UV QC + Fix All

One click checks the whole layout and gives a PASS / WARN / FAIL verdict. You can select the faces behind every issue, fix them automatically and save a JSON report for your pipeline.

Broken layout: overlaps, a fold, islands outside 0-1

Fix All: FAIL → PASS

Select an issue to see exactly which faces are affected

How to use

1. Open the UV QC panel. Choose the scope: All Faces or Selected.
2. Click Run UV Check. Each issue is listed with a count.
3. Click the arrow next to an issue to select its faces in the 3D Viewport and the UV Editor.
4. Click Fix All. RectiPack unwraps missing UVs, re-unwraps folded islands, then repacks and checks again. Intended stacks and priority factors are kept.
5. Click Export QC Report to save a .json next to your .blend.

◑ Texel density & stretch heatmap

A live overlay in the 3D Viewport and the UV Editor shows where density is too low (blue) or too high (red). After packing, everything turns green.

Three boxes at three densities

One pack later: 100% within ±20%

How to use

1. Open the Heatmap panel and pick Texel Density or Stretch.
2. Reference Median compares against the area-weighted median; Target compares against your Target TD.
3. The panel and the on-screen legend show the reference px/m and the share of surface within ±20%.
4. Use the 3D View / UV Editor toggles and Opacity to frame it. Cycle Off → TD → Stretch from the pie menu.

⤢ Unwrap First

Meshes without UVs work too. RectiPack unwraps them before straightening and packing, still in one click.

Barrel with no UV map: unwrapped, straightened and packed

How to use

1. Select a mesh without UVs and keep Unwrap on Auto in the Straighten panel.
2. Click Straighten & Pack. The report notes the unwrap.
3. For boxy hard-surface parts, try Seams by Angle, which cuts only sharp edges.

＋ More tools

⌨ Shortcuts & menus

• Shift+Alt+U opens the pie menu in Edit Mode, in both the 3D Viewport and the UV Editor. Its slots are Straighten & Pack, Straighten, Pack, UV Check, Stack, Add to Layout, Orient and Heatmap. Remap it in Preferences → Add-ons → UV RectiPack.
• The main commands are also at the bottom of the UV menu (UV Editor) and the U menu (3D Viewport).
• After any RectiPack button, open Adjust Last Operation (F9) to change options and see the result update live.

◇ Demo scenes included

RectiPack_Test_Scenes.blend is included. It has one ready-made scene per feature: straighten, pack, stack, Smart Priority, broken UVs for QC, a heatmap scene, a mesh without UVs, a non-square band, Add to Layout and Partial Grids. Each scene is labelled in the viewport, and a README text block in the file explains what to click.

? FAQ

Does it replace Blender's unwrap?

No. It works on top of any unwrap: seams, Smart UV Project or other add-ons. With Unwrap First it can also unwrap for you.

Will it mess up my pinned or finished UVs?

Only the selected faces are processed. Islands with pinned UVs are skipped when Keep Pinned is on, and Add to Layout never moves existing islands. Every operation is one Ctrl+Z.

Why is the TD lower than before on a fresh Smart UV layout?

Smart UV packs with 0 px margins. RectiPack adds mip-safe margins, and the report says so.

Are the islands packed as rectangles?

Yes. That is ideal for straightened and hard-surface UVs. Other islands are oriented to their tightest box first.

How fast is it?

Under a second for a typical prop. 800+ islands take a few seconds, because it is pure Python.

UDIM?

Not in 1.0. Each material packs into its own 0-1 space.

✓ Compatibility

Version 1.0.0 · © 2026 Dawid Gerula