add doc

README.md

@@ -358,7 +358,7 @@ These examples incubate dotSCAD and dotSCAD refactors these examples. See [examp
 [**triangle/tri_circumcenter**(shape_pts)](https://openhome.cc/eGossip/OpenSCAD/lib3x-tri_circumcenter.html) | return the circumcenter of a triangle.
 [**triangle/tri_incenter**(shape_pts)](https://openhome.cc/eGossip/OpenSCAD/lib3x-tri_incenter.html) | return the incenter of a triangle.
 [**triangle/tri_ear_clipping**(shape_pts,  ret = "TRI_INDICES", ...)](https://openhome.cc/eGossip/OpenSCAD/lib3x-tri_ear_clipping.html) | triangulation by [ear clipping](https://en.wikipedia.org/wiki/Polygon_triangulation#Ear_clipping_method).
-**triangle/tri_delaunay**(points, ret = "TRI_INDICES") | return the [Delaunay triangulation](https://en.wikipedia.org/wiki/Delaunay_triangulation) of the points.
+[**triangle/tri_delaunay**(points, ret = "TRI_INDICES")](https://openhome.cc/eGossip/OpenSCAD/lib3x-tri_delaunay.html) | Join a set of points to make a [Delaunay triangulation](https://en.wikipedia.org/wiki/Delaunay_triangulation).
 **triangle/tri_delaunay_indices**(d) | return triangle indices from a delaunay object.
 **triangle/tri_delaunay_shapes**(d) | return triangle shapes from a delaunay object.
 **triangle/tri_delaunay_voronoi**(d) | return [Voronoi](https://en.wikipedia.org/wiki/Voronoi_diagram) cells from a delaunay object.

docs/lib3x-tri_delaunay.md

@@ -0,0 +1,38 @@
+# tri_delaunay
+
+Join a set of points to make a [Delaunay triangulation](https://en.wikipedia.org/wiki/Delaunay_triangulation).
+
+**Since:** 3.0
+
+## Parameters
+
+- `points` : A list of points.
+- `ret` : The type of returned data. Default to `"TRI_INDICES"` which returns the indices of the `points`. `"TRI_SHAPES"` returns triangle shapes. `"VORONOI_CELLS"` returns voronoi cells. `"DELAUNAY"` returns a delaunay object which can be processed by [`tri_delaunay_indices`](lib3x-tri_delaunay_indices.html), [`tri_delaunay_shapes`](lib3x-tri_delaunay_shapes.html) and [`tri_delaunay_voronoi`](lib3x-tri_delaunay_voronoi.html).  
+
+## Examples
+
+    use <triangle/tri_delaunay.scad>;
+    use <hull_polyline2d.scad>;
+
+    points = [for(i = [0:20]) rands(-100, 100, 2)]; 
+
+    tris = [for(ti = tri_delaunay(points)) [for(i = ti) points[i]]];
+	linear_extrude(1)
+	for(t = tri_delaunay(points, ret = "TRI_SHAPES")) {
+		polygon(t);
+	}	
+	
+	color("black")
+	linear_extrude(2)
+	for(t = tri_delaunay(points, ret = "TRI_SHAPES")) {
+	    offset(-1)
+		    polygon(t);
+	}	
+	
+	color("red")
+	linear_extrude(3)
+	for(t = tri_delaunay(points, ret = "VORONOI_CELLS")) {
+	    hull_polyline2d(concat(t, [t[0]]), 2);
+	}
+
+![tri_delaunay](images/lib3x-tri_delaunay-1.JPG)

src/experimental/demo/tri_delaunay_demo.scad

@@ -1,13 +0,0 @@
-use <triangle/tri_delaunay.scad>;
-use <hull_polyline2d.scad>;
-
-points = [for(i = [0:20]) rands(-100, 100, 2)]; 
-
-draw([for(ti = tri_delaunay(points)) [for(i = ti) points[i]]]);
-%draw(tri_delaunay(points, ret = "TRI_SHAPES"));
-
-module draw(pointsOfTriangles) {
-	for(t = pointsOfTriangles) {
-	    hull_polyline2d(concat(t, [t[0]]));
-	}	
-}

src/triangle/tri_delaunay.scad

@@ -1,3 +1,13 @@
+/**
+* tri_circumcenter.scad
+*
+* @copyright Justin Lin, 2021
+* @license https://opensource.org/licenses/lgpl-3.0.html
+*
+* @see https://openhome.cc/eGossip/OpenSCAD/lib3x-tri_delaunay.html
+*
+**/
+
 use <_impl/_tri_delaunay_impl.scad>;
 use <tri_delaunay_shapes.scad>;
 use <tri_delaunay_indices.scad>;