add tri_subdivide

src/experimental/tri_subdivide.scad

@@ -0,0 +1,19 @@
+function _tri_subdivide(points) =
+     let(
+	     p0 = points[0],
+		 p1 = points[1],
+		 p2 = points[2],
+		 m0 = (p0 + p1) / 2,
+		 m1 = (p1 + p2) / 2,
+		 m2 = (p2 + p0) / 2
+	 )
+	 [
+	     [p0, m0, m2],
+		 [m0, p1, m1],
+		 [m1, p2, m2],
+		 [m0, m1, m2]
+	 ]; 
+
+function tri_subdivide(points, n = 1) =
+    n == 1 ? _tri_subdivide(points) :
+	[for(tri = tri_subdivide(points, n - 1)) each _tri_subdivide(tri)];