PersistentTrails.MeshFactory.getOrCreateMiddlePoint C# (CSharp) Method

        private static int getOrCreateMiddlePoint(int p1, int p2, ref List<Vector3> vertices, ref Dictionary<Int64, int> midPointCache)
        {
            // first check if we have it already
            bool firstIsSmaller = p1 < p2;
            Int64 smallerIndex = firstIsSmaller ? p1 : p2;
            Int64 greaterIndex = firstIsSmaller ? p2 : p1;
            Int64 key = (smallerIndex << 32) + greaterIndex;

            int ret;
            if (midPointCache.TryGetValue(key, out ret))
            {
                return ret;
            }

            // not in cache, calculate it
            Vector3 point1 = vertices[p1];
            Vector3 point2 = vertices[p2];
            Vector3 middle = new Vector3(
                (point1.x + point2.x) / 2.0f,
                (point1.y + point2.y) / 2.0f,
                (point1.z + point2.z) / 2.0f);

            // add vertex makes sure point is on unit sphere
            vertices.Add(middle.normalized);
            int index = vertices.Count -1;

            // store it, return index
            midPointCache.Add(key, index);
            return index;
        }