static Triangle[] CreateOctahedron ()
{
List<Triangle> shape = new List<Triangle>();
shape.Add( new Triangle( Vector3.UnitX, Vector3.UnitY, Vector3.UnitZ ) );
shape.Add( new Triangle( Vector3.UnitZ, Vector3.UnitY, -Vector3.UnitX ) );
shape.Add( new Triangle( -Vector3.UnitX, Vector3.UnitY, -Vector3.UnitZ ) );
shape.Add( new Triangle( -Vector3.UnitZ, Vector3.UnitY, Vector3.UnitX ) );
shape.Add( new Triangle( Vector3.UnitZ, -Vector3.UnitY, Vector3.UnitX ) );
shape.Add( new Triangle( -Vector3.UnitX, -Vector3.UnitY, Vector3.UnitZ ) );
shape.Add( new Triangle( -Vector3.UnitZ, -Vector3.UnitY, -Vector3.UnitX ) );
shape.Add( new Triangle( Vector3.UnitX, -Vector3.UnitY, -Vector3.UnitZ ) );
return shape.ToArray();
}