From c6ca52aba8b89df5bf1002e05c4bc0c02bc6c949 Mon Sep 17 00:00:00 2001
From: Justin Lin <justin.sdk@gmail.com>
Date: Fri, 3 Sep 2021 11:18:03 +0800
Subject: [PATCH] add r_union2

---
 src/experimental/r_union2.scad | 145 +++++++++++++++++++++++++++++++++
 1 file changed, 145 insertions(+)
 create mode 100644 src/experimental/r_union2.scad

diff --git a/src/experimental/r_union2.scad b/src/experimental/r_union2.scad
new file mode 100644
index 00000000..0fc67dfc
--- /dev/null
+++ b/src/experimental/r_union2.scad
@@ -0,0 +1,145 @@
+use <__comm__/__frags.scad>;
+
+module r_union2(r = 1) {
+	module _r_union2(r = 1) {
+	    fn = __frags(r);
+		step = 90 / fn;
+		rx = is_list(r) ? r[1] : r;
+		ry = is_list(r) ? r[0] : r;
+		
+		for(i = [0:fn - 1]) {
+			x = rx - sin(i * step) * rx;
+			y = ry - cos(i * step) * ry;
+			xi = rx - sin(i * step + step) * rx;
+			yi = ry - cos(i * step + step) * ry;
+			hull() {
+				intersection() {
+					offset(x) children(0);
+					offset(y) children(1);
+				}
+				intersection() {
+					offset(xi) children(0);
+					offset(yi) children(1);
+				}
+			}
+		}
+		
+		children(0);
+		children(1);
+	}
+	
+    if($children == 0) {
+	    // nope
+	}
+	else if($children == 1) {
+	    children(0);
+	}
+	else if($children == 2) {
+	    _r_union2(r) {
+			children(0);
+			children(1);
+		};
+	}
+	// OpenSCAD have to enumerate children explicitly.
+    // Currently, this module allow 10 children.
+	else if($children == 3) {
+	    r_union2(r) {
+			_r_union2(r) {
+				children(0);
+				children(1);
+			};
+			children(2);
+		}
+	}
+	else if($children == 4) {
+	    r_union2(r) {
+			_r_union2(r) {
+				children(0);
+				children(1);
+			};
+			children(2);
+			children(3);
+		}
+	}
+	else if($children == 5) {
+	    r_union2(r) {
+			_r_union2(r) {
+				children(0);
+				children(1);
+			};
+			children(2);
+			children(3);
+			children(4);
+		}
+	}
+	else if($children == 6) {
+	    r_union2(r) {
+			_r_union2(r) {
+				children(0);
+				children(1);
+			};
+			children(2);
+			children(3);
+			children(4);
+			children(5);
+		}
+	}
+	else if($children == 7) {
+	    r_union2(r) {
+			_r_union2(r) {
+				children(0);
+				children(1);
+			};
+			children(2);
+			children(3);
+			children(4);
+			children(5);
+			children(6);
+		}
+	}
+	else if($children == 8) {
+	    r_union2(r) {
+			_r_union2(r) {
+				children(0);
+				children(1);
+			};
+			children(2);
+			children(3);
+			children(4);
+			children(5);
+			children(6);
+			children(7);
+		}
+	}
+	else if($children == 9) {
+	    r_union2(r) {
+			_r_union2(r) {
+				children(0);
+				children(1);
+			};
+			children(2);
+			children(3);
+			children(4);
+			children(5);
+			children(6);
+			children(7);
+			children(8);
+		}
+	}
+	else if($children == 10) {
+	    r_union2(r) {
+			_r_union2(r) {
+				children(0);
+				children(1);
+			};
+			children(2);
+			children(3);
+			children(4);
+			children(5);
+			children(6);
+			children(7);
+			children(8);
+			children(9);
+		}
+	}
+}
\ No newline at end of file