public void ColinearityTest()
{
var a = new XbimVector3D(1, 0, 0);
var b = new XbimVector3D(0.5, 0, 0);
var ident = a.Angle(a);
Assert.AreEqual(0, ident, 1e-9);
var angle = a.Angle(b);
Assert.AreEqual(0, angle, 1e-9);
b = new XbimVector3D(1, 1, 0);
angle = a.Angle(b);
Assert.AreEqual(Math.PI / 4.0, angle, 1e-9);
b = new XbimVector3D(0, 1, 0);
angle = a.Angle(b);
Assert.AreEqual(Math.PI / 2.0, angle, 1e-9);
b = new XbimVector3D(-1, 1, 0);
angle = a.Angle(b);
Assert.AreEqual(Math.PI * 3.0 / 4.0, angle, 1e-9);
b = new XbimVector3D(-1, 0, 0);
angle = a.Angle(b);
Assert.AreEqual(Math.PI, angle, 1e-9);
b = new XbimVector3D(1, -1, 0);
angle = a.Angle(b);
Assert.AreEqual(Math.PI / 4.0, angle, 1e-9);
b = new XbimVector3D(-1, -1, 0);
angle = a.Angle(b);
Assert.AreEqual(Math.PI * 3.0 / 4.0, angle, 1e-9);
}