move

examples/spiral/simple_seashell.scad

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+use <shape_circle.scad>;
+use <ptf/ptf_rotate.scad>;
+use <sweep.scad>;
+
+r1 = 0.1;
+r2 = 50;
+
+a1 = 1;
+a2 = 450;
+
+steps = 40;
+
+$fn = 48;
+
+module simple_seashell(r1, r2, a1, a2, steps) {
+    rd = (r2 - r1) / steps;
+    ad = (a2 - a1) / steps;
+
+    sections = [
+        for (i = [0:steps])
+        let(
+            r = r1 + rd * i,
+            a = a1 + i * ad
+        )
+        [
+            for(p = concat(shape_circle(r), shape_circle(r * 0.9))) 
+                ptf_rotate([p[0], p[1], 0] + [r, 0, 0], [0, a, 0])
+        ]    
+            
+    ];
+
+    rotate([90, 0, 0]) sweep(sections, "HOLLOW");
+}
+
+simple_seashell(r1, r2, a1, a2, steps);