public void TestSidePoint()
{
// polygons to intersect with
Polygon3D s1 = new Polygon3D(new List <Point3D> {
s1_1, s1_2, s1_3, s1_4
}, "s2");
Polygon3D s2 = new Polygon3D(new List <Point3D> {
s1_1, s1_4, s1_3, s1_2
}, "s2"); // reverse order => swap surfaces
// point "on surface" of the square
Point3D p1 = new Point3D(1, 1, 0);
double z = p1.Z + (MSystem.SideDist * s1.Normal.Z); // calculate Z for assert purposes
Point3D res_s1_a = s1.SidePoint(p1, Tile.SideType.inside);
Point3D res_s1_b = s1.SidePoint(p1, Tile.SideType.outside);
Assert.AreEqual(res_s1_a.X, p1.X);
Assert.AreEqual(res_s1_a.Y, p1.Y);
Assert.AreEqual(res_s1_a.Z, z);
Assert.AreEqual(res_s1_a.X, res_s1_b.X);
Assert.AreEqual(res_s1_a.Y, res_s1_b.Y);
Assert.AreEqual(res_s1_a.Z, -(res_s1_b.Z)); // a bit nasty as we started with Z=0 => test is OK, if Z <> 0 the this would fail
Point3D res_s2_a = s2.SidePoint(p1, Tile.SideType.inside);
Point3D res_s2_b = s2.SidePoint(p1, Tile.SideType.outside);
Assert.AreEqual(res_s2_a, res_s1_b);
Assert.AreEqual(res_s2_b, res_s1_a);
// point "on edge" of the square
p1 = new Point3D(1, 0, 0);
z = p1.Z + (MSystem.SideDist * s1.Normal.Z); // calculate Z for assert purposes
res_s1_a = s1.SidePoint(p1, Tile.SideType.inside);
res_s1_b = s1.SidePoint(p1, Tile.SideType.outside);
Assert.AreEqual(res_s1_a.X, p1.X);
Assert.AreEqual(res_s1_a.Y, p1.Y);
Assert.AreEqual(res_s1_a.Z, z);
Assert.AreEqual(res_s1_a.X, res_s1_b.X);
Assert.AreEqual(res_s1_a.Y, res_s1_b.Y);
Assert.AreEqual(res_s1_a.Z, -(res_s1_b.Z));
res_s2_a = s2.SidePoint(p1, Tile.SideType.inside);
res_s2_b = s2.SidePoint(p1, Tile.SideType.outside);
Assert.AreEqual(res_s2_a, res_s1_b);
Assert.AreEqual(res_s2_b, res_s1_a);
// point "not on the surface square" of the square but this is valid
p1 = new Point3D(1, 1, 1);
z = p1.Z + (MSystem.SideDist * s1.Normal.Z); // calculate Z for assert purposes
res_s1_a = s1.SidePoint(p1, Tile.SideType.inside);
res_s1_b = s1.SidePoint(p1, Tile.SideType.outside);
Assert.AreEqual(res_s1_a.X, p1.X);
Assert.AreEqual(res_s1_a.Y, p1.Y);
Assert.AreEqual(res_s1_a.Z, z);
Assert.AreEqual(res_s1_a.X, res_s1_b.X);
Assert.AreEqual(res_s1_a.Y, res_s1_b.Y);
// z-coordinates shall not be apart more than this calculation
z = 2 * (MSystem.SideDist * Math.Abs(s1.Normal.Z));
Assert.AreEqual(z, res_s1_b.Z - res_s1_a.Z, MSystem.Tolerance);
res_s2_a = s2.SidePoint(p1, Tile.SideType.inside);
res_s2_b = s2.SidePoint(p1, Tile.SideType.outside);
Assert.AreEqual(res_s2_a, res_s1_b);
Assert.AreEqual(res_s2_b, res_s1_a);
}