1 files changed, 66 insertions, 0 deletions
diff --git a/graphics/asymptote/examples/dragon.asy b/graphics/asymptote/examples/dragon.asy
new file mode 100644
index 0000000000..08fcb61f5c
--- /dev/null
+++ b/graphics/asymptote/examples/dragon.asy
@@ -0,0 +1,66 @@
+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);