add dancing_taiwan

examples/dancing_taiwan.scad

@@ -0,0 +1,69 @@
+include <trim_shape.scad>;
+include <bezier_curve.scad>;
+include <shape_taiwan.scad>;
+include <path_scaling_sections.scad>;
+include <polysections.scad>;
+include <rotate_p.scad>;
+include <bijection_offset.scad>;
+
+x1 = 4; // [-20:4]
+x2 = 3; // [-20:4]
+x3 = 4; // [-20:4]
+y1 = 20; 
+y2 = 40;
+y3 = 90;
+twist = -90;
+t_step = 0.1;
+
+module dancing_formosan(x1, x2, x3, y1, y2, y3, twist, t_step) {
+
+    function cal_sections(shapt_pts, edge_path, twist) =
+        let(
+            sects = path_scaling_sections(shapt_pts, edge_path),
+            leng = len(sects),
+            twist_step = twist / leng
+        )
+        [
+            for(i = [0:leng - 1]) 
+            [
+                for(p = sects[i]) 
+                    rotate_p(p, twist_step * i)        
+            ]
+        ];
+
+    taiwan = shape_taiwan(100, 0.6);
+    fst_pt = [13, 0, 0];
+
+    edge_path = bezier_curve(t_step, [
+        fst_pt,
+        fst_pt + [0, 0, 10],
+        fst_pt + [x1, 0, y1],
+        fst_pt + [x2, 0, 35],
+        fst_pt + [x3, 0, y2],
+        fst_pt + [0, 0, 55],
+        fst_pt + [0, 0, y3]
+    ]);
+
+
+    offseted = bijection_offset(taiwan, -2);
+
+    edge_paty2 = [for(p = edge_path) p + [-2, 0, 0]];
+    taiwan2 = trim_shape(offseted, 1, len(offseted) - 4);
+
+    sections = cal_sections(taiwan, edge_path, twist);
+    sections2 = cal_sections(taiwan2, edge_paty2, twist);
+
+    difference() {
+        polysections(sections);
+        polysections(sections2);
+    }
+
+    translate([0, 0, -2]) 
+        linear_extrude(2) 
+            rotate(twist - twist / len(sections)) 
+                polygon(taiwan);
+
+}
+
+dancing_formosan(x1, x2, x3, y1, y2, y3, twist, t_step);
+