Polyhedron Sketchpad

▶ Open the sketchpad — runs in the browser, nothing to install.

Draw on the faces of a convex polyhedron and see the drawing on its Schlegel diagram, or draw on the diagram and see it on the 3D solid.

Models

31 convex polyhedra: the 5 Platonic, 13 Archimedean and 13 Catalan solids.

How to use

Action	How
Draw	Left-drag in either view
Straight line	Line (L), then click the start and end points (or drag) in either view; Esc cancels. The line is straight in the view you draw it in
Turn a face to the front (3D)	Click it in either view
Rotate 3D / pan 2D	Right-drag, hold Space, or toggle Rotate/Pan
Zoom	Mouse wheel
Colours	Swatches or keys 1–6, plus a custom colour picker
Erase a stroke	Eraser (E)
Undo / redo	⌘Z / ⇧⌘Z
Change the diagram's outer face	Set outer face…, then click a face
Enlarge the inner faces	Spread slider (far right = straight edges), Eye slider
New drawing	New (N)
Saved drawings	My creations (H): open, rename, delete or search them
Back up / move to another browser	Export JSON / Import JSON
Images	Save PNGs

The outer face of the Schlegel diagram is everything outside its boundary, so its drawings appear in the shaded ring around the diagram (the face turned inside-out). Every drawing is a creation. It is saved automatically, as JSON in your browser's IndexedDB, each time you finish a stroke, so closing the tab loses nothing. A new drawing is first saved when you draw on it and gets a name like "Cube 3", which you can change under My creations. When the page opens it reopens your last creation. Picking a model from the menu opens your most recent drawing of that model. Creations live only in this browser: use Export JSON to keep a copy or move them elsewhere.

Files

• polyhedra.html — the app (uses Three.js from a CDN).
• models.js — polyhedron data, generated from .obj files.
• build_models.py — converts .obj files to models.js, keeping only closed convex polyhedra and dropping duplicates. It reads ../sgi_logo/models/*.obj; edit SRC to point at your own folder.