From 30f83865f1d2cf1352c097ea52171575e0aefd82 Mon Sep 17 00:00:00 2001
From: Justin Lin <justin.sdk@gmail.com>
Date: Thu, 26 Aug 2021 21:13:12 +0800
Subject: [PATCH] add tri_arc_path

---
 src/experimental/tri_arc_path.scad | 41 ++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)
 create mode 100644 src/experimental/tri_arc_path.scad

diff --git a/src/experimental/tri_arc_path.scad b/src/experimental/tri_arc_path.scad
new file mode 100644
index 00000000..1627fd0f
--- /dev/null
+++ b/src/experimental/tri_arc_path.scad
@@ -0,0 +1,41 @@
+use <__comm__/__frags.scad>;
+use <angle_between.scad>;
+use <triangle/tri_circumcenter.scad>;
+use <ptf/ptf_rotate.scad>;
+use <util/reverse.scad>;
+use <experimental/tri_is_ccw.scad>;
+
+function _tri_arc_ct_clk(shape_pts) = 
+    let(
+	    c = tri_circumcenter(shape_pts),
+		v0 = shape_pts[0] - c,
+		v2 = shape_pts[2] - c,
+		r = norm(v0),
+		v0_a = atan2(v0[1], v0[0]),
+		a = angle_between(v0, v2, ccw = true),
+		a_step = a / __frags(r)
+	)
+	[for(a = [0:a_step:a]) c + ptf_rotate([r * cos(a), r * sin(a)], v0_a)];
+
+function tri_arc_path(shape_pts) = 
+    tri_is_ccw(shape_pts) ? 
+	    _tri_arc_ct_clk(shape_pts) : 
+		reverse(_tri_arc_ct_clk(reverse(shape_pts)));
+
+/*
+use <experimental/tri_arc_path.scad>;
+
+use <util/zip.scad>;
+use <hull_polyline2d.scad>;
+
+$fn = 24;
+pts = zip([rands(0, 20, 3), rands(0, 20, 3)]);
+
+hull_polyline2d(tri_arc_path(pts));
+#for(i = [0:len(pts) - 1]) {
+    translate(pts[i])
+	    sphere(1);
+    translate(pts[i])
+	    text(str(i), 2);
+}
+*/
\ No newline at end of file