From 6affac09a721d098bdd9f3b564f97b25926590c8 Mon Sep 17 00:00:00 2001
From: Justin Lin <justin.sdk@gmail.com>
Date: Tue, 31 May 2022 15:50:25 +0800
Subject: [PATCH] add tri_subdivide

---
 src/experimental/tri_subdivide.scad | 39 +++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)
 create mode 100644 src/experimental/tri_subdivide.scad

diff --git a/src/experimental/tri_subdivide.scad b/src/experimental/tri_subdivide.scad
new file mode 100644
index 00000000..83da68ab
--- /dev/null
+++ b/src/experimental/tri_subdivide.scad
@@ -0,0 +1,39 @@
+function _tri_subdivide_pts(points, n) = 
+   let(
+		p0 = points[0],
+		basis = [points[2] - p0, points[1] - p0] / n,
+        pts = [
+		    for(ri = [0:n], ci = [0:n - ri])
+		    p0 + [ri, ci] * basis
+        ]
+   )
+   pts;
+   
+function _tri_subdivide_indices(n) = 
+    let(
+		ri_base = [for(ri = 0, row_2 = n + 2; ri <= n; ri = ri + 1) ri * row_2 - ri * (ri + 1) * 0.5]
+    )
+    [
+		for(ri = [0:n - 1])
+			let(cols = n - ri - 1, base_i = ri_base[ri], base_i1 = ri_base[ri + 1])
+			for(ci = [0:cols]) 
+			let(ci_base_i = ci + base_i, ci_base_i1 = ci + base_i1, ci_base_i_1 = ci_base_i + 1)
+			if(ci != cols)
+				each [
+					[ci_base_i_1, ci_base_i1, ci_base_i], 
+					[ci_base_i1 + 1, ci_base_i1, ci_base_i_1]
+				]
+			else 
+				[ci_base_i_1, ci_base_i1, ci_base_i]
+	];
+    
+function tri_subdivide(tri, n) =
+    let(
+        pts = _tri_subdivide_pts(tri, n),
+        indices = _tri_subdivide_indices(n)
+    )
+    [
+        for(ti = indices) 
+        [pts[ti[0]], pts[ti[1]], pts[ti[2]]]
+    ];
+    
\ No newline at end of file