private static int MAX_TRIES = 5;
private static Vector3[] m_pathCorners = new Vector3[MAX_CORNERS];
private static NavMeshPath m_navMeshPath = new NavMeshPath();

//----------------------------------------------------------------------------------------
public static bool GetNavMeshPosition(Vector3 _pos, int _areaMask, float _maxDistance, out Vector3 _navMeshPos)
{
    NavMeshHit navMeshHit;
    if (NavMesh.SamplePosition(_pos, out navMeshHit, _maxDistance, _areaMask))
    {
        _navMeshPos = navMeshHit.position;
        return true;
    }
    _navMeshPos = Vector3.negativeInfinity;
    return false;
}

//----------------------------------------------------------------------------------------
public static int CalculatePath(Vector3 _start, Vector3 _target, NavMeshQueryFilter _filter, Vector3[] _path, int _startIndex = 0, int _numTries = 0)
{
    if (_numTries > MAX_TRIES || _startIndex >= m_pathCorners.Length)
    {
        if (_numTries > MAX_TRIES)
            Debug.Log("could not find a way from" + _start + " to " + _target + " in " + _numTries);
        else
            Debug.Log("could not find a way from" + _start + " to " + _target + " as" +_startIndex + "is samller or equal than" + m_pathCorners.Length);
        return -1;
    }

    var startPosOk = GetNavMeshPosition(_start, _filter.areaMask, MAX_PATH_DISTANCE, out Vector3 startPos);
    var endPosOk = GetNavMeshPosition(_target, _filter.areaMask, MAX_PATH_DISTANCE, out Vector3 targetPos);

    if (!startPosOk || !endPosOk)
    {
        Debug.Log("calculate path could not get proper navmesh position of start "+ _start  + " and/or target position " + _target);
        return -1;
    }

    NavMesh.CalculatePath(startPos, targetPos, _filter, m_navMeshPath);
    switch (m_navMeshPath.status)
    {
        case NavMeshPathStatus.PathPartial:
        {
            var numCorners = m_navMeshPath.GetCornersNonAlloc(m_pathCorners);
            Array.Copy(m_pathCorners, 0, _path, _startIndex, numCorners);
            var lastPos = m_navMeshPath.corners[m_navMeshPath.corners.Length - 1];
            if (Math.Abs(lastPos.x - targetPos.x) < 0.5f && Math.Abs(lastPos.z - targetPos.z) < 0.5f)
                return _startIndex + numCorners;

            return CalculatePath(lastPos, _target, _filter, _path, _startIndex + numCorners, ++_numTries);
        }
        case NavMeshPathStatus.PathComplete:
        {
            var numCorners = m_navMeshPath.GetCornersNonAlloc(m_pathCorners);
            Array.Copy(m_pathCorners, 0, _path, _startIndex, numCorners);
            return _startIndex + numCorners;
        }
        default:
        {
#if DEBUG
            Debug.Log("path invalid" + _start + " to " + _target + " in " + _numTries + " filter: " + _filter.areaMask);
#endif
            return -1;
        }
    }
}