NavMesh名字、层索引、层值之间的转换

    // 获取对象当前所站立的层值，1、2、4、8、16
    public static int GetAgentLayer(NavMeshAgent agent)
    {
        NavMeshHit hit;
        bool reach = NavMesh.SamplePosition(agent.transform.position, out hit, agent.radius, agent.walkableMask);
        return hit.mask;
    }

    // Nav层名字-->层索引（第几位），0、1、2、3、4
    public static int AgentLayerNameToIndex(string name)
    {
        return NavMesh.GetNavMeshLayerFromName(name);
    }

    // Nav层名字-->层的值，1、2、4、8、16
    public static int AgentLayerNameToValue(string name)
    {
        int idx = NavMesh.GetNavMeshLayerFromName(name);
        return (int)Mathf.Pow(2, idx);
    }

    // 检查对象某个层是否为开启
    public static bool IsNavMeshLayerOpen(NavMeshAgent agent, string layerName)
    {
        int layerValue = NavMesh.GetNavMeshLayerFromName(layerName);
        if (layerValue == -1)
            return true;

        int ret = agent.walkableMask & (0x1 << layerValue);
        return ret > 0 ? true : false;
    }

     // 开启某导航层
    public static void EnableNavMeshLayer(NavMeshAgent agent, string layerName)
    {
        if (agent == null)
            return;

        int layerValue = NavMesh.GetNavMeshLayerFromName(layerName);
        if (layerValue == -1)
            return;

        int mask = agent.walkableMask | 0x1 << layerValue;
        agent.walkableMask = mask;;
    }

    // 关闭某导航层
    public static void DisableNavMeshLayer(NavMeshAgent agent, string layerName)
    {
        if (agent == null)
            return;

        int layerValue = NavMesh.GetNavMeshLayerFromName(layerName);
        if (layerValue == -1)
            return;

        int mask = agent.walkableMask & ~(0x1 << layerValue);

        agent.walkableMask = mask;;
    }