public void Difference_between_square_p_and_square_q_contained_in_p_results_in_p_with_q_added_as_a_hole_contour()
{
var corner1 = new Vector2(0.1, 0.2);
var side1 = 4.5;
var bigPolygon = (Polygon)Square(corner1, side1, positive: true);
var corner2 = new Vector2(0.9, 0.8);
var side2 = 2.3;
var smallPolygon = (Polygon)Square(corner2, side2, positive: true);
var result = PolygonUtils.Difference(bigPolygon, smallPolygon);
Expect(result.Contours.Count, Is.EqualTo(2));
var contour0 = result.Contours.ElementAt(0);
var contour1 = result.Contours.ElementAt(1);
Expect(Math.Sign(contour0.SignedArea()) != Math.Sign(contour1.SignedArea()));
var outContour = contour0.SignedArea() > 0 ? contour0 : contour1;
var inContour = contour0.SignedArea() > 0 ? contour1 : contour0;
Expect(outContour.Vertices.Count, Is.EqualTo(bigPolygon.CountVertices()));
Expect(outContour.SignedArea(), Is.EqualTo(bigPolygon.Area()).Within(_tolerance));
Expect(inContour.Vertices.Count, Is.EqualTo(smallPolygon.CountVertices()));
Expect(inContour.SignedArea(), Is.EqualTo(-smallPolygon.Area()).Within(_tolerance));
}
private void ExpectPolygonsAreEqualWithinTolerance(IPolygon p, IPolygon q, double tolerance)
{
var pMinusQ = PolygonUtils.Difference(p, q);
var qMinusP = PolygonUtils.Difference(q, p);
Expect(qMinusP.Area(), Is.LessThan(tolerance));
Expect(pMinusQ.Area(), Is.LessThan(tolerance));
}
public void Difference_of_two_empty_polygons_is_empty()
{
var p = Polygon.Empty;
var q = Polygon.Empty;
var result = PolygonUtils.Difference(p, q);
Expect(result.IsEmpty);
}
public void Intersection_of_3_rectangles_yields_the_correct_square()
{
var rectangles = new List <IPolygon>
{
new Box2(minX: 0, minY: 0, width: 2, height: 2),
new Box2(minX: -1, minY: -1, width: 4, height: 2),
new Box2(minX: -1, minY: -1, width: 2, height: 4)
};
var result = PolygonUtils.Intersection(rectangles);
Expect(result.IsSimple);
Expect(result.CountVertices(), Is.EqualTo(4));
Expect(result.Area(), Is.EqualTo(1).Within(_tolerance));
var resultBox = result.BoundingBox();
Expect(PolygonUtils.Difference(resultBox, result).Area(), Is.EqualTo(0).Within(_tolerance));
Expect(resultBox.Width, Is.EqualTo(1).Within(_tolerance));
Expect(resultBox.Height, Is.EqualTo(1).Within(_tolerance));
Expect(resultBox.MinCorner.X, Is.EqualTo(0).Within(_tolerance));
Expect(resultBox.MinCorner.Y, Is.EqualTo(0).Within(_tolerance));
}
private IPolygon MakeHoleIn(IPolygon p)
{
var hole = new Box2(minX: 1, minY: 1, width: 1, height: 1);
return(PolygonUtils.Difference(p, hole));
}