private static void rngTriangleAreaTest()
{
var rng = new FastRng();
var a = new PointXY(rng.Exclusive(-1.0, 1.0), rng.Exclusive(0.0, 1.0));
var b = new PointXY(rng.Exclusive(1.0, 2.0), rng.Exclusive(-2.0, -1.0));
var c = new PointXY(rng.Exclusive(-2.0, -1.0), rng.Exclusive(-2.0, -1.0));
var bc = new PointXY(new[] { b, c }.Average());
var inside = new PointXY(new [] { a, bc }.Average());
Assert.IsTrue(inside.InsideTriangle(new List <IPoint>(new [] { a, b, c })));
var areaA = Triangle.Area(b, c, inside);
Assert.Less(Math.Abs(areaA - Triangle.Area(c, b, inside)), 1e-12);
Assert.Less(Math.Abs(areaA - Triangle.Area(inside, b, c)), 1e-12);
Assert.Less(Math.Abs(areaA - Triangle.Area(c, inside, b)), 1e-12);
var areaB = Triangle.Area(a, c, inside);
Assert.Less(Math.Abs(areaB - Triangle.Area(c, a, inside)), 1e-12);
Assert.Less(Math.Abs(areaB - Triangle.Area(inside, a, c)), 1e-12);
Assert.Less(Math.Abs(areaB - Triangle.Area(c, inside, a)), 1e-12);
var areaC = Triangle.Area(a, b, inside);
Assert.Less(Math.Abs(areaC - Triangle.Area(b, a, inside)), 1e-12);
Assert.Less(Math.Abs(areaC - Triangle.Area(inside, a, b)), 1e-12);
Assert.Less(Math.Abs(areaC - Triangle.Area(b, inside, a)), 1e-12);
var area = Triangle.Area(a, b, c);
Assert.Less(Math.Abs(area - Triangle.Area(b, a, c)), 1e-12);
Assert.Less(Math.Abs(area - Triangle.Area(c, a, b)), 1e-12);
Assert.Less(Math.Abs(area - Triangle.Area(b, c, a)), 1e-12);
Assert.Less(Math.Abs(area - (areaA + areaB + areaC)), 1e-12);
}
public void InsideTriangleTest()
{
var rng = new FastRng();
for (int i = 2; i < 100; i++)
{
var a = new PointXY(rng.Exclusive(-100.0, 100.0), rng.Exclusive(-100.0, 100.0));
var b = new PointXY(rng.Exclusive(-100.0, 100.0), rng.Exclusive(-100.0, 100.0));
var c = new PointXY(rng.Exclusive(-100.0, 100.0), rng.Exclusive(-100.0, 100.0));
var midpointBC = new PointXY((b.X + c.X) / (2.0), (b.Y + c.Y) / (2.0));
var insidePoint = new PointXY((midpointBC.X + a.X) / (2.0), (midpointBC.Y + a.Y) / (2.0));
Assert.IsTrue(insidePoint.InsideTriangle(a, b, c));
var dx = midpointBC.X - a.X;
var dy = midpointBC.Y - a.Y;
// outside point, past BC on a->midpointBC vector.
// As i increases, point is closer to to midpoint of BC
var outsidePoint = new PointXY((midpointBC.X + dx / i), (midpointBC.Y + dy / i));
Assert.IsFalse(outsidePoint.InsideTriangle(a, b, c));
var dxy = new Vector(midpointBC.X - a.X, midpointBC.Y - a.Y);
var outside = new PointXY(midpointBC + dxy / i);
Assert.IsFalse(outside.InsideTriangle(a, b, c));
// inside point, inside BC on a->midpointBC vector
// As i increases, point is closer to midpoint of BC
insidePoint = new PointXY((midpointBC.X - dx / i), (midpointBC.Y - dy / i));
Assert.IsTrue(insidePoint.InsideTriangle(a, b, c));
var inside = new PointXY(midpointBC - dxy / i);
Assert.IsTrue(inside.InsideTriangle(c, b, a));
}
}