commit

chenxin

2020-11-19 95ed512ab8ec6ae3fc5bb827cb0e3fe98adc44d3

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using UnityEngine;
using UnityEngine.AI;
 
namespace TowerDefense.Agents
{
    /// <summary>
    /// Agent that can pass "over" towers that block the path
    /// </summary>
    public class FlyingAgent : Agent
    {
        /// <summary>
        /// Time to wait to clear the navmesh obstacles
        /// </summary>
        protected float m_WaitTime = 0.5f;
 
        /// <summary>
        /// The current time to wait until we can resume agent movement as normal
        /// </summary>
        protected float m_CurrentWaitTime;
 
        /// <summary>
        /// If flying agents are blocked, they should still move through obstacles
        /// </summary>
        protected override void OnPartialPathUpdate()
        {
            if (!isPathBlocked)
            {
                state = State.OnCompletePath;
                return;
            }
            if (!isAtDestination)
            {
                return;
            }
            m_NavMeshAgent.enabled = false;
            m_CurrentWaitTime = m_WaitTime;
            state = State.PushingThrough;
        }
        
        /// <summary>
        /// Controls behaviour based on the states <see cref="Agent.State.OnCompletePath"/>, <see cref="Agent.State.OnPartialPath"/> 
        /// and <see cref="Agent.State.PushingThrough"/>
        /// </summary>
        protected override void PathUpdate()
        {
            switch (state)
            {
                case State.OnCompletePath:
                    OnCompletePathUpdate();
                    break;
                case State.OnPartialPath:
                    OnPartialPathUpdate();
                    break;
                case State.PushingThrough:
                    PushingThrough();
                    break;
            }
        }
 
        /// <summary>
        /// When flying agents are pushing through, give them a small amount of time to clear the gap and turn on their agent
        /// once time elapses
        /// </summary>
        protected void PushingThrough()
        {
            m_CurrentWaitTime -= Time.deltaTime;
 
            // Move the agent, overriding its NavMeshAgent until it reaches its destination
            transform.LookAt(m_Destination.transform, Vector3.up);
            transform.position += transform.forward * m_NavMeshAgent.speed * Time.deltaTime;
            if (m_CurrentWaitTime > 0)
            {
                return;
            }
            // Check if there is a navmesh under the agent, if not, then reset the timer
            NavMeshHit hit;
            if (!NavMesh.Raycast(transform.position + Vector3.up, Vector3.down, out hit, navMeshMask))
            {
                m_CurrentWaitTime = m_WaitTime;
            }
            else
            {
                // If the time elapses, and there is a NavMesh under it, resume agent movement as normal
                m_NavMeshAgent.enabled = true;
                NavigateTo(m_Destination.transform.position);
                state = isPathBlocked ? State.OnPartialPath : State.OnCompletePath;
            }
        }
    }
}