From a754b15d0316440c5ec998e895696560267dbf0f Mon Sep 17 00:00:00 2001
From: Justin Lin <caterpillar@openhome.cc>
Date: Sun, 30 Apr 2017 14:30:49 +0800
Subject: [PATCH] added polysections

---
 src/polysections.scad | 64 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 src/polysections.scad

diff --git a/src/polysections.scad b/src/polysections.scad
new file mode 100644
index 00000000..c55d0dc9
--- /dev/null
+++ b/src/polysections.scad
@@ -0,0 +1,64 @@
+module polysections(sections, triangles = "RADIAL") {
+    module tri_sections(tri1, tri2) {
+        polyhedron(
+            points = concat(tri1, tri2),
+            faces = concat(
+                [[0, 1, 2]],
+                [[3, 4, 5]],
+                [for(i = [0:2]) [i, (i + 1) % 3, (i + 1) % 3 + 3]],
+                [for(i = [0:2]) [i, i % 3 + 3, (i + 1) % 3 + 3]]
+            )
+        );  
+    }
+    
+    function flat(vector, i = 0) =
+        i == len(vector) ? [] :
+        concat(vector[i], flat(vector, i + 1));    
+    
+    leng_section = len(sections[0]);
+    
+    function radial_tris() = [
+        for(i = [1:leng_section - 2]) [0, i, i + 1]
+    ];
+        
+    function hollow_tris() = 
+        let(
+            inner_i_begin = leng_section / 2,
+            pair_idxes = [for(i = [0:inner_i_begin - 1])
+                let(n = inner_i_begin + i + 1)
+                [
+                    [i, inner_i_begin + i, n % inner_i_begin + inner_i_begin], 
+                    [i, i + 1, n % leng_section]
+                ]
+                
+            ]
+           
+        ) flat(pair_idxes); 
+
+    function tris() = triangles == "RADIAL" ? radial_tris() : 
+        (triangles == "HOLLOW" ? hollow_tris() : triangles);
+    
+    module two_sections(section1, section2) {
+        for(idx = tris()) {
+            hull() tri_sections(
+                [
+                    section1[idx[0]], 
+                    section1[idx[1]], 
+                    section1[idx[2]]
+                ], 
+                [
+                    section2[idx[0]], 
+                    section2[idx[1]], 
+                    section2[idx[2]]
+                ]
+            );
+        }
+    }
+    
+    for(i = [0:len(sections) - 2]) {
+         two_sections(
+             sections[i], 
+             sections[i + 1]
+         );
+    }
+}
\ No newline at end of file