🀄 Wallpaper Symmetry Groups
About this simulation
A wallpaper group is a mathematical classification of the repeating symmetry patterns that can tile the infinite plane using combinations of translation, rotation, reflection and glide reflection. In 1891 the crystallographer Evgraf Fedorov proved that exactly 17 such groups exist — no more, no fewer — a landmark result connecting geometry, group theory and crystallography. This simulation implements a simplified but mathematically correct subset of 9 of those 17 groups (p1, p2, pm, pg, cm, p4, p4m, p6, p6m), constructed directly from their symmetry operations rather than approximated visually.
How it works
- An asymmetric motif is placed at an off-center anchor point inside one lattice cell, so it never accidentally has extra symmetry of its own.
- For the chosen group, the motif is duplicated by the group's point-group operations (rotation and/or reflection about the cell's symmetry center) to build one "cluster" of copies.
- That whole cluster is then repeated across the canvas by pure translation along the group's lattice vectors — a square lattice for p1–p4m, or a hexagonal lattice for p6 and p6m.
- The optional overlay draws schematic markers: circles at rotation centers (color-coded by rotation order), dashed lines for true mirror axes, and dash-dot lines for glide reflection axes.
Key equations
A point p is rotated about center c by angle θ via p′ = c + R(θ)·(p−c), and reflected across a line through c at angle α via p′ = c + M(2α)·(p−c), where R and M are the standard 2×2 rotation and reflection matrices. A glide reflection composes a reflection with a translation of half a lattice period along the mirror axis. Every wallpaper pattern is then p(x) = p(x + m·e₁ + n·e₂) for integers m, n and lattice vectors e₁, e₂.
Controls
- Wallpaper group — choose which of the 9 implemented groups to render.
- Motif — switch between the L-shape, flag and dot+line asymmetric motifs.
- Cell size — zoom in or out by changing the lattice cell size in pixels.
- Symmetry overlay — show or hide the schematic rotation-center and mirror/glide-axis markers.
Did you know?
All 17 wallpaper groups appear in the geometric tilings of the Alhambra palace in Granada, Spain — centuries before the classification theorem was proved. M. C. Escher independently rediscovered many of the same symmetry principles in his interlocking prints after studying Moorish tilework. Today the same 17-group classification underlies how crystallographers describe the symmetry of two-dimensional atomic layers and surface structures.