add fidget_star

examples/spiral_polygons/fidget_star.scad

@@ -0,0 +1,68 @@
+use <shape_starburst.scad>;
+
+r1 = 12;
+r2 = 8;
+n = 6;
+number_of_stars = 10;
+height = 20;
+thickness = 1.5;
+spacing = 0.5 * thickness;
+slope = 0.375;
+
+/*
+r1 = 12;
+r2 = 9.55;
+n = 8;
+number_of_stars = 10;
+height = 20;
+thickness = 1.5;
+spacing = 0.5 * thickness;
+slope = 0.25;
+*/
+
+fidget_star(r1, r2, n, number_of_stars, height, thickness, spacing, slope);
+	
+module fidget_star(r1, r2, n, number_of_stars, height, thickness, spacing, slope) {
+    theta = 180 / n;
+
+	y = r2 - r2 * cos(theta);
+	dr = y / cos(theta) + thickness + spacing;
+	pw = pow((r2 + dr) * sin(theta), 2);
+	
+	r_ratio = r1 / r2;
+
+	module drawPolygon(r1, r2) {
+	    polygon(shape_starburst(r1, r2, n));
+	}
+	
+	rs2 = [for(i = [0: number_of_stars + 1]) r2 + i * dr];
+	rs1 = rs2 * r_ratio;
+	
+	half_height = height / 2;
+
+	s = [for(i = [1: number_of_stars + 1]) (rs2[i] + slope * half_height) / rs2[i]];
+
+	module half() {
+	    translate([0, 0, -half_height]) {
+			linear_extrude(half_height, scale = s[0])
+			difference() {
+				drawPolygon(r1, r2);
+				offset(delta = -thickness)
+				    drawPolygon(r1, r2);
+			}
+				
+			for(i = [1:number_of_stars - 1]) {
+				linear_extrude(half_height, scale = s[i])
+				difference() {
+					drawPolygon(rs1[i], rs2[i]);
+					offset(delta = -thickness)
+					    drawPolygon(rs1[i], rs2[i]);
+				}					
+			}
+		}
+	}
+	
+	half();	
+	mirror([0, 0, 1])
+		half();
+}