diff --git a/src/surface/sf_solidify_tri.scad b/src/surface/sf_solidify_tri.scad
new file mode 100644
index 00000000..a23744f6
--- /dev/null
+++ b/src/surface/sf_solidify_tri.scad
@@ -0,0 +1,82 @@
+use <util/set/hashset.scad>;
+use <util/set/hashset_has.scad>;
+use <util/set/hashset_add.scad>;
+use <util/set/hashset_del.scad>;
+use <util/set/hashset_elems.scad>;
+
+module sf_solidify_tri(points1, points2, triangles) {
+    // triangles : clockwise
+    leng = len(points1);
+	assert(leng == len(points2), "The length of points1 must equal to the length of points2");
+		
+	function de_pairs(tri_edges) = 
+		let(
+			leng = len(tri_edges),
+			edges = hashset([tri_edges[0], tri_edges[1], tri_edges[2]], number_of_buckets = round(sqrt(leng)))
+		)
+		_de_pairs(tri_edges, leng, edges);
+		
+	function _de_pairs(tri_edges, leng, edges, i = 3) =
+		i == leng ? hashset_elems(edges) :
+		let(edge = tri_edges[i], pair = [edge[1], edge[0]])
+		hashset_has(edges, pair) ? 
+			_de_pairs(tri_edges, leng, hashset_del(edges, pair), i + 1) :
+			_de_pairs(tri_edges, leng, hashset_add(edges, edge), i + 1);	
+			
+	tri_edges = [
+		for(tri = triangles)
+		each [
+			[tri[0], tri[1]],
+			[tri[1], tri[2]],
+			[tri[2], tri[0]]
+		]
+	];	
+	
+	edges = de_pairs(tri_edges);
+	side_faces = [
+	    for(edge = edges)
+		each [
+		    [edge[1] + leng, edge[1], edge[0]],
+			[edge[0] + leng, edge[1] + leng, edge[0]]
+		]
+	];
+	
+	points = concat(points1, points2);
+	faces = concat(
+	    triangles, 
+		[for(tri = triangles) [tri[2], tri[1], tri[0]] + [leng, leng, leng]],
+		side_faces
+	);
+	
+	polyhedron(points = points, faces = faces);
+}
+
+/*
+use <triangle/tri_delaunay.scad>;
+use <triangle/tri_delaunay_indices.scad>;
+use <triangle/tri_delaunay_shapes.scad>;
+
+use <surface/sf_solidify_tri.scad>;
+
+points = [for(i = [0:50]) rands(-200, 200, 2)]; 
+
+delaunay = tri_delaunay(points, ret = "DELAUNAY");
+
+// count-clockwise (dotSCAD 2D polygon convention)
+indices = tri_delaunay_indices(delaunay);
+shapes = tri_delaunay_shapes(delaunay);
+
+
+for(t = shapes) {
+    offset(-1)
+        polygon(t);
+}
+
+pts = [for(p = points) [p[0], p[1], rands(100, 150, 1)[0]]];
+pts2 = [for(p = pts) [p[0], p[1], p[2] - 10]];
+
+// triangles: clockwise (openscad 3D face convention)
+sf_solidify_tri(pts, pts2, 
+    triangles = [for(tri = indices) [tri[2], tri[1], tri[0]]]);	
+
+*/
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