add shape_star

src/_impl/_shape_star_impl.scad

@@ -0,0 +1,20 @@
+function __outer_points_shape_star(r1, r2, n) = 
+    let(
+        a = 360 / n
+    )
+    [for(i = 0; i < n; i = i + 1) [r1 * cos(90 + a * i), r1 * sin(90 + a * i)]];
+
+function __inner_points_shape_star(r1, r2, n) = 
+    let (
+        a = 360 / n,
+        half_a = a / 2
+    )
+    [for(i = 0; i < n; i = i + 1) [r2 * cos(90 + a * i + half_a), r2 * sin(90 + a * i + half_a)]];
+    
+function _shape_star_impl(r1, r2, n) = 
+   let(
+       outer_points = __outer_points_shape_star(r1, r2, n),
+       inner_points = __inner_points_shape_star(r1, r2, n),
+       leng = len(outer_points)
+    )
+   [for(i = 0; i < leng; i = i + 1) each [outer_points[i], inner_points[i]]];

src/shape_star.scad

@@ -0,0 +1,13 @@
+/**
+* shape_star.scad
+*
+* @copyright Justin Lin, 2021
+* @license https://opensource.org/licenses/lgpl-3.0.html
+*
+* @see https://openhome.cc/eGossip/OpenSCAD/lib3x-shape_star.html
+*
+**/
+
+use <_impl/_shape_star_impl.scad>;
+
+function shape_star(outerRadius = 1, innerRadius = 0.381966, n = 5) = _shape_star_impl(outerRadius, innerRadius, n);