From a1686c4feafa85bdc2958540f69455010adf7ed1 Mon Sep 17 00:00:00 2001
From: Justin Lin <caterpillar@openhome.cc>
Date: Sun, 20 Sep 2020 17:41:18 +0800
Subject: [PATCH] y offset

---
 examples/string_tetrahedron.scad | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/examples/string_tetrahedron.scad b/examples/string_tetrahedron.scad
index 113bed9d..2d6dfbb9 100644
--- a/examples/string_tetrahedron.scad
+++ b/examples/string_tetrahedron.scad
@@ -29,10 +29,11 @@ function height(leng) =
 function vts(leng) = 
     let(
         half_leng = leng / 2,
-        vt1 = [half_leng, 0, 0],
-        vt2 = [0, leng * sin(60), 0],
-        vt3 = [-half_leng, 0, 0],
-        vt4 = [0, half_leng * tan(30), height(leng)]
+        center_y = half_leng * tan(30),
+        vt1 = [half_leng, - center_y, 0],
+        vt2 = [0, leng * sin(60) - center_y, 0],
+        vt3 = [-half_leng, -center_y, 0],
+        vt4 = [0, 0, height(leng)]
     ) [vt1, vt2, vt3, vt4];
 
 module string_tetrahedron(leng, thickness, segs_per_side, line_fn) {