lathe/test/spec/polygon2d.test.js

A discrete solid modeller using BSPs

define([
    'lib/plane2d', 
    'lib/vertex2d', 
    'lib/polygon2d'
  ], function(Plane2D, Vertex2D,  Polygon2D) {

    describe('2D Polygons', function() {

      it('can be constructed from a plane and bounding planes', function() {

        var bounding = [
          new Plane2D(1,0,0),
          new Plane2D(0,1,0),
          new Plane2D(1,1,1),
        ];
        var polygon = new Polygon2D(bounding);

        var vertices = polygon.toVertices();
        assert.equal(vertices.length, 3);

        var xy = new Plane2D(1,1,1);
        var x0 = new Plane2D(1,0,0);
        var y0 = new Plane2D(0,1,0);

        assert.deepEqual(vertices[0], new Vertex2D(xy, x0));
        assert.deepEqual(vertices[1], new Vertex2D(x0, y0));
        assert.deepEqual(vertices[2], new Vertex2D(y0, xy));

      });

      it('can be split by a plane', function() {

        var bounding = [
          new Plane2D(1,0,1),
          new Plane2D(0,1,1),
          new Plane2D(1,0,-1),
          new Plane2D(0,1,-1)
        ];
        var polygon = new Polygon2D(bounding);

        var result1 = polygon.splitBy(new Plane2D(1,0,-1));
        var result2 = polygon.splitBy(new Plane2D(1,0,1));
        var result3 = polygon.splitBy(new Plane2D(1,0,0));

        // Coincident and same orientation
        assert.deepEqual(result1.front, polygon);
        assert.isUndefined(result1.back);

        // Coincident and different orientation
        assert.isUndefined(result2.front);
        assert.deepEqual(result2.back, polygon);

        // Square split by y=0 plane
        assert.deepEqual(result3.front, new Polygon2D(
          [
            new Plane2D(1, 0,  1),
            new Plane2D(0, 1,  1),
            new Plane2D(1, 0,  0),
            new Plane2D(0, 1, -1),
          ]));
      });

    });

  });