A haXe port of the General Polygon Clipper (GPC) library developed by Alan Murta

Homepage: http://www.cs.manchester.ac.uk/~toby/alan/software/

GPC license http://www.cs.manchester.ac.uk/~toby/alan/software/#Licensing

GPC is free for non-commercial use ONLY. If you wish to use GPC in support of a commercial product, you must obtain an official GPC Commercial Use Licence from The University of Manchester.

About

GPC is part of the motor library and can be found in the package de.polygonal.motor.geom.gpc.

It consists of merely two classes: GPC.hx (API), the clipping algorithm and GPCPolygon.hx (API), which is a data structure that is used by the GPC class to describe polygons (both input & clipped polygons).

Examples

Great Britain and Arrows example from GPC homepage ("GPC in Action")

Great Britain and Arrows example (animated)

The source files of the examples can be found here. To compile them run $ haxe compile.hxml in the gpc folder.

Usage

Here is a simple example that computes the union of two bounding boxes:

import de.polygonal.gl.VectorRenderer;
import de.polygonal.gl.Window;
import de.polygonal.motor.geom.gpc.GPC;
import de.polygonal.motor.geom.gpc.GPCPolygon;
import de.polygonal.motor.geom.primitive.AABB2;

class SimpleExample
{
    public static function main() {
        Window.initBackgroundColor = 0xffffff;
        de.polygonal.core.Root.init(onInit, true);
    }
    
    static function onInit() {
        
        //the input shapes
        var box1 = new AABB2(100, 100, 200, 200);
        var box2 = new AABB2(150, 150, 250, 250);
        
        //define first input polygon
        var input1 = new GPCPolygon();
        input1.addContour(box1.getVertexListScalar(new Array<Float>()), 8);
        
        //define second input polygon
        var input2 = new GPCPolygon();
        input2.addContour(box2.getVertexListScalar(new Array<Float>()), 8);
        
        //define output polygon
        var output = new GPCPolygon();
        
        //compute union of input1 and input
        GPC.clip(input1, input2, output, ClipOperation.Union);
        
        var vr = new VectorRenderer();
        
        //draw input
        vr.setLineStyle();
        vr.aabb(box1);
        vr.aabb(box2);
        
        //draw output
        vr.setLineStyle(0xff0000, .5, 4);
        for (contour in output) vr.polyLineScalar(contour.getArray(), true, contour.size());
        
        //draw everything
        vr.flush(Window.surface.graphics);

        //release memory used by GPC class (if never used again)
        GPC.free();
    }
}