How to Use Origami Simulator to Fold and Export a Crease Pattern

Updated

Open origamisimulator.org in a WebGL-capable browser, load a crease pattern from the Examples menu or upload your own SVG/FOLD file, then drag the Fold Percent slider to fold it. The simulator folds every crease simultaneously rather than in sequential steps: 100% is fully folded, 0% is flat, and -100% is fully folded with mountain and valley assignments reversed. Drag to rotate the model and scroll to zoom. When the folded shape looks right, use File > Save Simulation as... to export a FOLD file or an STL/OBJ 3D model.

Before You Start

  • Browser: The app is a real-time WebGL application, so you need a browser with WebGL support. All rendering and 3D interaction run on three.js.
  • Input format: Crease patterns must be in SVG or FOLD format. The site links to its own import instructions, which are worth reading before your first upload — curved crease patterns in particular are pre-processed with a ruling-aware triangulation method so the bending between creases looks realistic.
  • What "folding" means here: The solver iteratively computes small displacements of an initially flat sheet caused by crease forces, running in parallel GPU fragment shaders. You are watching a physical relaxation, not a step-by-step folding animation, so the motion can look organic rather than instructional.

Step-by-Step: Fold a Pattern

  1. Load a pattern. Open the Examples menu and pick a built-in crease pattern, or upload your own SVG/FOLD file. Starting with an example is the fastest way to confirm the app is rendering correctly on your machine.
  2. Set the fold degree. Slide Fold Percent to any value between -100 and 100. Watch how the sheet moves: intermediate values show partially folded states, which is useful for spotting creases that behave unexpectedly.
  3. Inspect the shape. Drag to rotate the model and scroll to zoom. Check both sides of the sheet — a reversed mountain/valley assignment is easiest to catch by comparing the 100% and -100% states.
  4. Check strain (optional). Open Advanced Options in the left menu and turn on Strain Visualization to see internal strain as the pattern folds. This helps identify regions where the crease pattern is fighting itself.
  5. Export. Choose File > Save Simulation as... and pick FOLD for the crease/simulation data, or STL/OBJ for the folded 3D geometry.

Expected Results and How to Verify

  • At 0% the sheet should appear flat; at 100% it should reach its fully folded state. If it doesn't, the pattern likely has inconsistent mountain/valley assignments or geometry the solver can't resolve.
  • If the model doesn't move at all, confirm the page finished loading and that your browser has WebGL enabled.
  • If an uploaded SVG looks distorted, compare it against a built-in example at the same Fold Percent — the difference usually points to a parsing or scale issue in the file rather than the simulator.

Importing Your Own Crease Patterns

Upload SVG or FOLD files directly in the app, following the site's linked import instructions. Two practical notes:

  • SVG path parsing is handled by svgpath and path-data-polyfill, so standard SVG path data is the safest bet.
  • Curved folds are supported through the triangulation pre-processing mentioned above, but expect the result to be an approximation of the bend rather than an exact physical model.

If you have a crease pattern that would make a good demo, the site invites submissions to the Examples menu by email (the address is on the author's website).

Exporting: Which Format to Choose

Format Use it when What you get
FOLD You want to keep the simulation/crease data, re-import it, or share the pattern with other FOLD-compatible tools Structured crease-pattern and simulation data
STL You need a mesh for 3D printing or mesh-based software Folded-state 3D geometry
OBJ You need a mesh for rendering, animation, or modeling tools that prefer OBJ Folded-state 3D geometry

Export captures the folded state of your design, so set Fold Percent to the state you want before saving.

Common Snags

  • The model won't fold smoothly. Try intermediate Fold Percent values to see where it stalls; the strain visualization often shows the problem area.
  • Negative Fold Percent looks wrong. That's expected behavior — it flips mountain/valley assignments, so a pattern that looks correct at 100% will look inverted at -100%.
  • VR mode: The site notes instructions for using the app with a VR headset and hand controllers, but also flags that this mode may now be deprecated. Don't plan a workflow around it without testing first.

Background, If You Want to Go Deeper

The simulator was originally built by Amanda Ghassaei as a final project for Geometric Folding Algorithms, with contributors including Sasaki Kosuke and Erik Demaine. The method is described in Fast, Interactive Origami Simulation using GPU Computation (Ghassaei, Demaine, Gershenfeld, 7OSME), and the solver extends work by Mark Schenk and Simon D. Guest and by Tomohiro Tachi. Source code is available on GitHub.