Wallpaper Groups
The 17 wallpaper groups — all possible ways to tile a plane with a repeating pattern. Shader implementations.
*442 (p4m)
Square lattice with 4-fold rotation at cell centers and corners, plus mirror lines along diagonals and edges.
vec2 uv = (FC.xy * 2. - r) / min(r.x, r.y) * 2.5;
uv = 1. - abs(fract(uv * .5) * 2. - 1.);
if (uv.y > uv.x) uv = uv.yx;
o.rg += uv.xy;
o *= step(.3, uv.y + uv.x);
o *= step(.04, uv.y);