add convex_offset

src/experimental/convex_offset.scad

@@ -0,0 +1,21 @@
+use <triangle/tri_incenter.scad>;
+
+function convex_offset(vertices, d) = 
+    let(
+	    c = tri_incenter(vertices),
+		leng_vertices = len(vertices)
+	)
+    [
+	    for(i = [0:leng_vertices - 1]) 
+	    let(
+		    curr_p = vertices[i],
+			next_p = vertices[(i + 1) % leng_vertices],
+		    v1 = c - curr_p,
+			v2 = next_p - curr_p,
+			leng_v1 = norm(v1),
+			leng_v2 = norm(v2),
+			a = acos((v1 * v2) / (leng_v1 * leng_v2)),
+			leng = -d / sin(a) 
+		)
+		v1 / leng_v1 * leng + curr_p
+    ];