added polytransversals

README.md

@@ -32,6 +32,7 @@ Some modules may depend on other modules. For example, the `polyline2d` module d
 	- [circular_sector](https://openhome.cc/eGossip/OpenSCAD/lib-circular_sector.html)
 	- [arc](https://openhome.cc/eGossip/OpenSCAD/lib-arc.html)
 	- [hexagons](https://openhome.cc/eGossip/OpenSCAD/lib-hexagons.html)
+	- [polytransversals](https://openhome.cc/eGossip/OpenSCAD/lib-polytransversals.html)
 
 - 3D
 	- [rounded_cube](https://openhome.cc/eGossip/OpenSCAD/lib-rounded_cube.html)

docs/lib-polytransversals.md

@@ -0,0 +1,42 @@
+# polytransversals
+
+Crosscutting a polyline at different points gets several transversals. This module can operate reversely. It uses transversals to construct a polyline. For example, imagine that you have the following transversals:
+
+![polytransversals](images/lib-polytransversals-1.JPG)
+
+This module can use them to construct the polyline:
+
+![polytransversals](images/lib-polytransversals-2.JPG)
+
+When using this module, you should use points to represent each transversal. 
+
+You can view it as a better polyline2d module. If you have only the points of a path, using `polyline2d` or `hull_polyline2d` is a simple solution. If you know the transversals along a path, you can use `polytransversals` to get a better polyline.
+
+## Parameters
+
+- `transversals` : A list of transversals. Each transversal is represented by a list of points. See the example below.
+
+## Examples
+
+	include <rotate_p.scad>;
+	include <polytransversals.scad>;
+	include <hull_polyline2d.scad>;
+	
+	r = 35;    
+	tran_pts = [[-5, 0], [0, 5], [5, 0]];
+	
+	trans = [
+	    for(a = [0:10:120])
+	        [
+	            for(p = tran_pts) 
+	                rotate_p(p, [0, 0, a]) + [r * cos(a), r * sin(a)]
+	        ]
+	];
+	
+	polytransversals(trans);
+	
+	#for(tran = trans) {
+	    hull_polyline2d(tran, 0.5);
+	}
+
+![polytransversals](images/lib-polytransversals-3.JPG)

src/polytransversals.scad

@@ -3,7 +3,6 @@
 *
 * Crosscutting a polyline at different points gets several transversals.
 * This module can operate reversely. It uses transversals to construct a polyline.
-*
 * @copyright Justin Lin, 2017
 * @license https://opensource.org/licenses/lgpl-3.0.html
 *