/// <summary>
        /// Rotates a triangle pair one vertex CW
        ///       n2                    n2
        ///  P +-----+             P +-----+
        ///    | t  /|               |\  t |
        ///    |   / |               | \   |
        ///  n1|  /  |n3           n1|  \  |n3
        ///    | /   |    after CW   |   \ |
        ///    |/ oT |               | oT \|
        ///    +-----+ oP            +-----+
        ///       n4                    n4
        /// </summary>
        private static void RotateTrianglePair(DelaunayTriangle t, TriangulationPoint p, DelaunayTriangle ot, TriangulationPoint op)
        {
            DelaunayTriangle n1, n2, n3, n4;

            n1 = t.NeighborCCWFrom(p);
            n2 = t.NeighborCWFrom(p);
            n3 = ot.NeighborCCWFrom(op);
            n4 = ot.NeighborCWFrom(op);

            bool ce1, ce2, ce3, ce4;

            ce1 = t.GetConstrainedEdgeCCW(p);
            ce2 = t.GetConstrainedEdgeCW(p);
            ce3 = ot.GetConstrainedEdgeCCW(op);
            ce4 = ot.GetConstrainedEdgeCW(op);

            bool de1, de2, de3, de4;

            de1 = t.GetDelaunayEdgeCCW(p);
            de2 = t.GetDelaunayEdgeCW(p);
            de3 = ot.GetDelaunayEdgeCCW(op);
            de4 = ot.GetDelaunayEdgeCW(op);

            t.Legalize(p, op);
            ot.Legalize(op, p);

            // Remap dEdge
            ot.SetDelaunayEdgeCCW(p, de1);
            t.SetDelaunayEdgeCW(p, de2);
            t.SetDelaunayEdgeCCW(op, de3);
            ot.SetDelaunayEdgeCW(op, de4);

            // Remap cEdge
            ot.SetConstrainedEdgeCCW(p, ce1);
            t.SetConstrainedEdgeCW(p, ce2);
            t.SetConstrainedEdgeCCW(op, ce3);
            ot.SetConstrainedEdgeCW(op, ce4);

            // Remap neighbors
            // XXX: might optimize the markNeighbor by keeping track of
            //      what side should be assigned to what neighbor after the
            //      rotation. Now mark neighbor does lots of testing to find
            //      the right side.
            t.Neighbors.Clear();
            ot.Neighbors.Clear();
            if (n1 != null)
            {
                ot.MarkNeighbor(n1);
            }
            if (n2 != null)
            {
                t.MarkNeighbor(n2);
            }
            if (n3 != null)
            {
                t.MarkNeighbor(n3);
            }
            if (n4 != null)
            {
                ot.MarkNeighbor(n4);
            }
            t.MarkNeighbor(ot);
        }