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The 3D Workshop

Every physical thing you can build from a 3D file comes down to one number: how many triangles. Twelve is a cube you can fold before your coffee cools. A few hundred is a life-size cardboard figure. Fifty thousand is a job only a machine can do. The four studios here — trace a photo into a solid, sculpt it point by point, then unfold it into numbered cut sheets or slice it into stackable ribs — all run free in your browser, and all stay inside the numbers a pair of hands can actually build.

How many triangles is buildable?
Slide up the ladder - somewhere between 12 and 69,451, a craft project becomes impossible.
292
The starter bunny

The famous Stanford bunny, redrawn at craft scale. It ships inside the unfolder studio as the built-in starter model - load it and unfold it with one click.

A weekend - and it’s pre-loaded

Tools in the workshop

LIVE
STL to Papercraft Unfolder
Import a low-poly STL or OBJ, push and pull the points in 3D, scale it to life size, and unfold it into numbered cut sheets for paper, cardboard or leadlight glass - plus an armature generator (ribs and rods) so big builds stand up. Free Pepakura alternative, no install.
Open the studio →
LIVE
STL Slicer
The discontinued 123D Make modes, rebuilt: stacked layers with dowel holes, or interlocked waffle ribs with half-lap slots. Real-size SVG per piece for laser, CNC or knife.
Open the studio →
LIVE
Image to STL
Loft a front silhouette and a side silhouette into a watertight low-poly solid - no AI, no upload. Exports STL or hands over to the unfolder in one click.
Open the studio →
LIVE
Point Sculptor
Start from nothing: drop points on a sliding plane inside a 1-metre cube and a watertight skin wraps them live. Imports XYZ point clouds, exports STL, hands over to the unfolder.
Open the studio →
NEW
Leadlight Designer
Drop in a photo or a scanned cartoon and get a stained-glass pattern: lead lines you can drag with the pieces following, every uncuttable piece flagged with a one-click fix, real came sizes, the fewest-cut came runs, and numbered full-size PDF sheets with a glass list. Free Glass Eye alternative.
Open the studio →
NEW
Leadlight In Place
Photograph the doorway or window, drag four corners onto the opening, and a panel drops in behind the photo at the same angle - stretched or slid to fit, lit from behind so the glass glows and the came goes dark, with the light spilling onto the wall. One picture to send the customer.
Open the studio →
LIVE
Reduce STL
Melt a heavy mesh down to an exact triangle count - watch triangles leave live, stop when the shape starts to suffer, scrub back up, export. Presets at 5,000 (phone ceiling), 800 (hand-build cap) and 292 (bunny scale).
Open the studio →
IN BUILD
More Workshop Tool
Contact us for any tool we forgot to give the STL 3D printer world.

The tools that used to exist

There was a golden moment when this was all free. Autodesk shipped 123D Make in 2011 — feed it a model, and it produced stacked slices with dowel holes, interlocking ribs, or folded panels, complete with numbered parts and assembly diagrams. In 2017 it became Slicer for Fusion 360; in 2020 Autodesk discontinued it outright, posting a final unsupported download and walking away. The paid survivors — Pepakura Designer on Windows, Unfolder on Mac — lock exporting behind a licence.

None of the underlying geometry ever needed a licence or an operating system. Unfolding is hinge-by-hinge trigonometry; slicing is a plane cutting triangles. A browser tab does both — so this workshop rebuilt them. The slicer brings back 123D Make’s stacked and interlocked modes; the unfolder does what Pepakura charges for. Every mode stays free, and the roadmap card above shows what gets rebuilt next.

Questions people actually ask

Is there a free alternative to Pepakura Designer?
Yes - the STL to Papercraft unfolder on this page runs in any browser, on any operating system, and exports numbered real-size cut sheets for free. Pepakura Designer is Windows-only and locks saving and exporting behind a paid licence key.
What replaced 123D Make and Slicer for Fusion 360?
Officially, nothing - Autodesk discontinued Slicer for Fusion 360 in 2020 and posted a final unsupported download. The STL Slicer here rebuilds its two most-used modes, stacked slices with dowel holes and interlocked waffle ribs, as a free browser tool.
How many triangles can you actually build by hand?
About 800 is the practical ceiling for scissors and glue. A 12-triangle cube takes minutes, a 250-300 triangle trophy takes a weekend, and past 800 the part count makes hand assembly punishing - that is machine territory.
Do these tools upload my 3D files anywhere?
No. Every tool in the workshop runs entirely inside your browser tab - parsing, editing, unfolding and slicing all happen on your own device, and your files never leave it. There is no signup and no account.
Sources
  • Autodesk support — Slicer for Fusion 360 deprecation notice and final 2020 release
  • Autodesk Community — 123D Make (2011) to Slicer for Fusion 360 (2017) lineage
  • Tamasoft — Pepakura Designer licensing (save/export disabled unregistered)
  • Stanford Computer Graphics Laboratory — the Stanford bunny, laser-scanned 1994, 69,451 triangles in the reconstructed mesh
  • STL format specification — 50 bytes per triangle; dental crown scans at 20,000–50,000 triangles ≈ 1 MB

Sixty-nine thousand triangles is a file. Two hundred and ninety-two is a rabbit on your desk. The whole workshop exists to get you from one number to the other.