Turn Any STL Into a Cut-and-Fold Pattern
For twenty years, turning a 3D model into something you could cut from paper meant one US$38 Windows program that locks saving until you pay. The geometry it does — unrolling triangles flat, one hinge at a time — runs fine in a browser. So here it is, free: import a low-poly STL, push the points around, scale it to life size, and unfold it into numbered patterns for paper, cardboard, or leadlight glass — with an armature generator so the big builds can stand up.
How unfolding actually works
An STL file is nothing but triangles — a binary STL literally begins with an 80-byte header followed by a 4-byte count of how many triangles follow, at 50 bytes each. Every pair of neighbouring triangles shares an edge, and a shared edge is a hinge. Unfolding picks one triangle, lays it flat, then swings each neighbour down around its hinge, and each neighbour's neighbour, until the whole surface lies in one plane — exactly like flattening a cardboard box.
The catch is overlap. Swing enough triangles down and eventually one lands on top of another. When that happens the pattern has to be cut into a separate piece — an island — and that is why every papercraft model comes as several parts with matching numbers along the cut edges. This tool numbers both halves of every cut for you: find edge 14, glue it to the other edge 14, and the model closes itself.
There is a practical ceiling. Hobbyists who have built these physically report that simple low-poly shapes fold up cleanly while dense scans like the Stanford bunny are effectively impossible to assemble by hand — which is why this studio caps imports at 800 faces rather than pretending a 50,000-triangle dental scan is a weekend craft project.
Paper, cardboard, or leadlight — three very different builds
Paper and card get glue tabs on every cut edge and fold-line styles for direction — the classic papercraft workflow. It suits models up to about half a metre; beyond that paper skin starts to sag under its own span.
Cardboard drops the tabs (tape and hot glue beat tabs at 3 mm thickness) and treats every fold line as a score line — run a blunt edge along it against a ruler before bending. This is the mode for a life-size figure, paired with the studio's armature generator: horizontal ribs cut from the model's own cross-sections, threaded on vertical rods, so the folded skin has a skeleton to sit on instead of collapsing under its own span.
Leadlight is the odd one out: no folds at all. Every triangle becomes its own separate pattern piece with its edge lengths printed in millimetres, because in stained-glass work the pieces are cut individually and joined with lead came — the came is the hinge. A low-poly form built this way becomes a three-dimensional glass sculpture, and pattern generators for that essentially do not exist anywhere else.
Why has this been paid software for 20 years?
Pepakura Designer, from Japanese developer Tamasoft, has owned this niche since the early 2000s — it is the tool behind most of the papercraft helmets and low-poly wall trophies on the internet. It is genuinely good software, but it is Windows-only and the unregistered version disables saving and exporting entirely, so actually producing a pattern means paying for a licence. Mac users have a separate paid app (Unfolder), and the free options have historically been rough: community tools that are slow on medium models and admit to producing inaccurate results by random chance.
Autodesk briefly gave everyone a free answer — 123D Make, later renamed Slicer for Fusion 360, which turned models into stacked slices, interlocked ribs and folded panels. Then Autodesk discontinued it in 2020 and never replaced it, leaving forum threads full of people hunting for alternatives. The geometry never got harder; the free tools just disappeared. That gap is exactly what this studio — and the workshop tools that will follow it — exists to fill.
- Tamasoft — Pepakura Designer overview and licensing (save/export disabled in the unregistered version)
- Autodesk support — Slicer for Fusion 360 deprecation notice, final release published August 2020
- Autodesk Community forums — "Fusion 360 Slicer Alternative" threads confirming 123D Make lineage and discontinuation
- Trammell Hudson, "Unfolding STL" — physical low-poly builds from matte board; assembly limits of dense meshes
- STL format specification — 80-byte binary header, 4-byte triangle count, 50 bytes per triangle