pair crease(pair z1, pair z2, bool left) { pair dz = z2 - z1; if (left) return z1 + dz * (0.5, 0.5); else return z1 + dz * (0.5, -0.5); } pair[] fold(pair[] oldz) { int n = oldz.length; pair[] newz = new pair[2n-1]; for (int i = 0; i < n-1; ++i) { newz[2i] = oldz[i]; newz[2i+1] = crease(oldz[i], oldz[i+1], i%2==0); } newz[2(n-1)] = oldz[n-1]; return newz; } pair[] dragon(int n, pair[] base={}) { if (base.length == 0) if (n%2 == 0) base = new pair[] {(0,0), (1,1) }; else base = new pair[] {(0,0), (1,0) }; pair[] z = base; for (int i = 1; i < n; ++i) z = fold(z); return z; } void drawtris(pair[] z, pen p = currentpen) { int n = z.length; for (int i = 0; i < n-2; i+=2) fill(z[i]--z[i+1]--z[i+2]--cycle, p); } void drawtris(pair[] z, pen p1, pen p2) { int n = z.length; for (int i = 0; i < n-2; i+=2) fill(z[i]--z[i+1]--z[i+2]--cycle, 2i < n-1 ? p1 : p2); } size(500,0); int n = 10; drawtris(dragon(n, new pair[] {(0,0), (1,0)}), black); drawtris(dragon(n, new pair[] {(0,0), (0,-1)}), blue); drawtris(dragon(n, new pair[] {(0,0), (-1,0)}), red); drawtris(dragon(n, new pair[] {(0,0), (0,1)}), green);