本文主要是介绍ML-Agents案例之跳墙游戏，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
本案例源自ML-Agents官方的示例，Github地址：https://github.com/Unity-Technologies/ml-agents
本文基于我前面发的两篇文章，需要对ML-Agents有一定的了解，详情请见：Unity强化学习之ML-Agents的使用、ML-Agents命令及配置大全。
本文主要的知识点是课程学习（Curriculum Learning）以及Model Override脚本的使用。
参考资料：ML-Agents（九）Wall Jump
环境说明
本案例环境较为简单，智能体的目标是到达绿色的目标点，但是中间会有堵墙相隔，墙的高度随机，当墙较矮时，智能体可以直接跳跃快速到达目标点，但是当墙体较高时，需要先推动方块进行垫脚，然后再跳过墙体。
和推箱子的案例类似，跳墙案例智能体的输入使用了射线传感器包括十四根射线，射线的作用在这里不再说明。
详情参考我前面的文章ML-Agents案例之推箱子游戏的单人模式。
除了使用传感器之外，agent脚本中还包含了目标到智能体的向量，和是否接触地面，这里有四维。
智能体的输出包含4个离散输出，第一个决定往前走，往后走，什么都不做。第二个决定往左走，在右走，什么都不做。第三个决定顺时针旋转，逆时针旋转，什么都不做。第四个决定了跳跃和什么都不做。
智能体脚本设定如下：
射线传感器检测的标签有三个：墙，方块，目标点。
脚本代码
本项目较简单，只有一个主要的agent脚本需要查看：
WallJumpAgent.cs
using System.Collections;
using UnityEngine;
using Unity.MLAgents;
using Unity.Barracuda;
using Unity.MLAgents.Actuators;
using Unity.MLAgents.Sensors;
using Unity.MLAgentsExamples;public class WallJumpAgent : Agent
{// Depending on this value, the wall will have different heightint m_Configuration;// 三个模型应用在三个不同情况// Brain to use when no wall is presentpublic NNModel noWallBrain;// Brain to use when a jumpable wall is presentpublic NNModel smallWallBrain;// Brain to use when a wall requiring a block to jump over is presentpublic NNModel bigWallBrain;public GameObject ground;public GameObject spawnArea;Bounds m_SpawnAreaBounds;public GameObject goal;public GameObject shortBlock;public GameObject wall;Rigidbody m_ShortBlockRb;Rigidbody m_AgentRb;Material m_GroundMaterial;Renderer m_GroundRenderer;WallJumpSettings m_WallJumpSettings;public float jumpingTime;public float jumpTime;// This is a downward force applied when falling to make jumps look// less floatypublic float fallingForce;// Use to check the coliding objectspublic Collider[] hitGroundColliders = new Collider[3];Vector3 m_JumpTargetPos;Vector3 m_JumpStartingPos;// 配置文件中设定的三个模型名字，实际这里只设定两个string m_NoWallBehaviorName = "SmallWallJump";string m_SmallWallBehaviorName = "SmallWallJump";string m_BigWallBehaviorName = "BigWallJump";EnvironmentParameters m_ResetParams;// 初始化public override void Initialize(){// 寻找设定参数的脚本m_WallJumpSettings = FindObjectOfType<WallJumpSettings>();// 随机墙的高度m_Configuration = Random.Range(0, 5);// 获取物体中的各种组件m_AgentRb = GetComponent<Rigidbody>();m_ShortBlockRb = shortBlock.GetComponent<Rigidbody>();m_SpawnAreaBounds = spawnArea.GetComponent<Collider>().bounds;m_GroundRenderer = ground.GetComponent<Renderer>();m_GroundMaterial = m_GroundRenderer.material;// 使生成区域不可见spawnArea.SetActive(false);// 获取配置参数m_ResetParams = Academy.Instance.EnvironmentParameters;// Update model references if we're overridingvar modelOverrider = GetComponent<ModelOverrider>();// 导入三个模型，采用配置文件的参数if (modelOverrider.HasOverrides){noWallBrain = modelOverrider.GetModelForBehaviorName(m_NoWallBehaviorName);m_NoWallBehaviorName = ModelOverrider.GetOverrideBehaviorName(m_NoWallBehaviorName);smallWallBrain = modelOverrider.GetModelForBehaviorName(m_SmallWallBehaviorName);m_SmallWallBehaviorName = ModelOverrider.GetOverrideBehaviorName(m_SmallWallBehaviorName);bigWallBrain = modelOverrider.GetModelForBehaviorName(m_BigWallBehaviorName);m_BigWallBehaviorName = ModelOverrider.GetOverrideBehaviorName(m_BigWallBehaviorName);}}// 设定跳跃参数public void Jump(){jumpingTime = 0.2f;m_JumpStartingPos = m_AgentRb.position;}// 判断是否接触地面，里面包含两种方式public bool DoGroundCheck(bool smallCheck){if (!smallCheck){hitGroundColliders = new Collider[3];var o = gameObject;// 这里给智能体设定一个盒子碰撞体，找到与其碰撞的碰撞体，返回// 参数分别是碰撞体中心，碰撞体每个维度的大小，返回的碰撞体，盒子的旋转。Physics.OverlapBoxNonAlloc(o.transform.position + new Vector3(0, -0.05f, 0),new Vector3(0.95f / 2f, 0.5f, 0.95f / 2f),hitGroundColliders,o.transform.rotation);var grounded = false;//如果检测到对应标签，则判断触地foreach (var col in hitGroundColliders){if (col != null && col.transform != transform &&(col.CompareTag("walkableSurface") ||col.CompareTag("block") ||col.CompareTag("wall"))){grounded = true; //then we're groundedbreak;}}return grounded;}else{// 射线检测方式检测触地RaycastHit hit;// 智能体往正下方发生射线,没有完全触地时会判断触Physics.Raycast(transform.position + new Vector3(0, -0.05f, 0), -Vector3.up, out hit,1f);// 射线检测到对应标签的物体代表触地if (hit.collider != null &&(hit.collider.CompareTag("walkableSurface") ||hit.collider.CompareTag("block") ||hit.collider.CompareTag("wall"))&& hit.normal.y > 0.95f){return true;}return false;}}// 顺滑地移动物体// 参数代表：终点，刚体，目标速度，最大速度void MoveTowards(Vector3 targetPos, Rigidbody rb, float targetVel, float maxVel){var moveToPos = targetPos - rb.worldCenterOfMass;var velocityTarget = Time.fixedDeltaTime * targetVel * moveToPos;if (float.IsNaN(velocityTarget.x) == false){// 在现在值和目标值中间选择一个值，不高于maxVelrb.velocity = Vector3.MoveTowards(rb.velocity, velocityTarget, maxVel);}}// 输入设定public override void CollectObservations(VectorSensor sensor){var agentPos = m_AgentRb.position - ground.transform.position;// 输入目标到智能体的向量sensor.AddObservation(agentPos / 20f);// 输入是否触地sensor.AddObservation(DoGroundCheck(true) ? 1 : 0);}// 在生成区域旋转一个位置生成方块public Vector3 GetRandomSpawnPos(){var randomPosX = Random.Range(-m_SpawnAreaBounds.extents.x,m_SpawnAreaBounds.extents.x);var randomPosZ = Random.Range(-m_SpawnAreaBounds.extents.z,m_SpawnAreaBounds.extents.z);var randomSpawnPos = spawnArea.transform.position +new Vector3(randomPosX, 0.45f, randomPosZ);return randomSpawnPos;}// 转换材质IEnumerator GoalScoredSwapGroundMaterial(Material mat, float time){m_GroundRenderer.material = mat;yield return new WaitForSeconds(time); //wait for 2 secm_GroundRenderer.material = m_GroundMaterial;}// 根据输出的值确定移动方式public void MoveAgent(ActionSegment<int> act){AddReward(-0.0005f);// 两种不同的检查方式（完全触地或离地较低）var smallGrounded = DoGroundCheck(true);var largeGrounded = DoGroundCheck(false);var dirToGo = Vector3.zero;var rotateDir = Vector3.zero;// 四个离散输出的赋值var dirToGoForwardAction = act[0];var rotateDirAction = act[1];var dirToGoSideAction = act[2];var jumpAction = act[3];// 根据离散输出计算响应的动作if (dirToGoForwardAction == 1)dirToGo = (largeGrounded ? 1f : 0.5f) * 1f * transform.forward;else if (dirToGoForwardAction == 2)dirToGo = (largeGrounded ? 1f : 0.5f) * -1f * transform.forward;if (rotateDirAction == 1)rotateDir = transform.up * -1f;else if (rotateDirAction == 2)rotateDir = transform.up * 1f;if (dirToGoSideAction == 1)dirToGo = (largeGrounded ? 1f : 0.5f) * -0.6f * transform.right;else if (dirToGoSideAction == 2)dirToGo = (largeGrounded ? 1f : 0.5f) * 0.6f * transform.right;if (jumpAction == 1)if ((jumpingTime <= 0f) && smallGrounded){Jump();}// 执行动作transform.Rotate(rotateDir, Time.fixedDeltaTime * 300f);m_AgentRb.AddForce(dirToGo * m_WallJumpSettings.agentRunSpeed,ForceMode.VelocityChange);// 跳跃尚未结束，往最高点移动if (jumpingTime > 0f){m_JumpTargetPos =new Vector3(m_AgentRb.position.x,m_JumpStartingPos.y + m_WallJumpSettings.agentJumpHeight,m_AgentRb.position.z) + dirToGo;MoveTowards(m_JumpTargetPos, m_AgentRb, m_WallJumpSettings.agentJumpVelocity,m_WallJumpSettings.agentJumpVelocityMaxChange);}// 在空中下坠时添加一个下坠的力if (!(jumpingTime > 0f) && !largeGrounded){m_AgentRb.AddForce(Vector3.down * fallingForce, ForceMode.Acceleration);}jumpingTime -= Time.fixedDeltaTime;}public override void OnActionReceived(ActionBuffers actionBuffers){MoveAgent(actionBuffers.DiscreteActions);// 智能体或方块掉下平台，扣分，重开if ((!Physics.Raycast(m_AgentRb.position, Vector3.down, 20))|| (!Physics.Raycast(m_ShortBlockRb.position, Vector3.down, 20))){SetReward(-1f);EndEpisode();ResetBlock(m_ShortBlockRb);StartCoroutine(GoalScoredSwapGroundMaterial(m_WallJumpSettings.failMaterial, .5f));}}public override void Heuristic(in ActionBuffers actionsOut){var discreteActionsOut = actionsOut.DiscreteActions;if (Input.GetKey(KeyCode.D)){discreteActionsOut[1] = 2;}if (Input.GetKey(KeyCode.W)){discreteActionsOut[0] = 1;}if (Input.GetKey(KeyCode.A)){discreteActionsOut[1] = 1;}if (Input.GetKey(KeyCode.S)){discreteActionsOut[0] = 2;}discreteActionsOut[3] = Input.GetKey(KeyCode.Space) ? 1 : 0;}// 接触到目标点，加分，重开void OnTriggerStay(Collider col){if (col.gameObject.CompareTag("goal") && DoGroundCheck(true)){SetReward(1f);EndEpisode();StartCoroutine(GoalScoredSwapGroundMaterial(m_WallJumpSettings.goalScoredMaterial, 2));}}// 重置物块void ResetBlock(Rigidbody blockRb){blockRb.transform.position = GetRandomSpawnPos();blockRb.velocity = Vector3.zero;blockRb.angularVelocity = Vector3.zero;}// 游戏开始时重置物块和智能体的位置public override void OnEpisodeBegin(){ResetBlock(m_ShortBlockRb);transform.localPosition = new Vector3(18 * (Random.value - 0.5f), 1, -12);m_Configuration = Random.Range(0, 5);m_AgentRb.velocity = default(Vector3);}void FixedUpdate(){// 每个episode设定一次墙高度if (m_Configuration != -1){ConfigureAgent(m_Configuration);m_Configuration = -1;}}// 设定墙高度，根据高度设定不同的模型void ConfigureAgent(int config){var localScale = wall.transform.localScale;if (config == 0){localScale = new Vector3(localScale.x,m_ResetParams.GetWithDefault("no_wall_height", 0),localScale.z);wall.transform.localScale = localScale;// 设定对应配置文件的Behavior Name以及对应模型SetModel(m_NoWallBehaviorName, noWallBrain);}else if (config == 1){// 在没有课程训练（Curriculum Learning）的配置下，值默认为4// 在有课程训练的配置下，墙的高度直接设为配置中的值，而这个值会随着训练而改变localScale = new Vector3(localScale.x,m_ResetParams.GetWithDefault("small_wall_height", 4),localScale.z);wall.transform.localScale = localScale;SetModel(m_SmallWallBehaviorName, smallWallBrain);}else{var height = m_ResetParams.GetWithDefault("big_wall_height", 8);localScale = new Vector3(localScale.x,height,localScale.z);wall.transform.localScale = localScale;SetModel(m_BigWallBehaviorName, bigWallBrain);}}
}注意这个案例终于用到了Override这个脚本，它的作用是在训练中也能通过SetModel(m_BigWallBehaviorName, bigWallBrain)替换模型，其中第一个参数是配置文件中的Behavior Name，第二个就是对应的模型文件。这样我们就能在不同的情况采用不同的模型了。
配置文件
配置文件1：PPO算法，于以往不同，可以看到我们配置了两个神经网络，一个名字是BigWallJump，一个是SmallWallJump。这是因为我们的环境需要给智能体配置两个神经网络，根据不同的情况调用不同的神经网络分别进行学习。因为一个神经网络如果要做的事情太多往往需要的训练时间很长，很可能train不起来。如果分成几个任务，适时调用不同的神经网络，不仅可以加快训练速度，还能达到更好的效果。
亲测这种算法在高墙时无法收敛，没办法利用方块，平均得分-0.6。
behaviors:BigWallJump:trainer_type: ppohyperparameters:batch_size: 128buffer_size: 2048learning_rate: 0.0003beta: 0.005epsilon: 0.2lambd: 0.95num_epoch: 3learning_rate_schedule: linearnetwork_settings:normalize: falsehidden_units: 256num_layers: 2vis_encode_type: simplereward_signals:extrinsic:gamma: 0.99strength: 1.0keep_checkpoints: 5max_steps: 20000000time_horizon: 128summary_freq: 20000SmallWallJump:trainer_type: ppohyperparameters:batch_size: 128buffer_size: 2048learning_rate: 0.0003beta: 0.005epsilon: 0.2lambd: 0.95num_epoch: 3learning_rate_schedule: linearnetwork_settings:normalize: falsehidden_units: 256num_layers: 2vis_encode_type: simplereward_signals:extrinsic:gamma: 0.99strength: 1.0keep_checkpoints: 5max_steps: 5000000time_horizon: 128summary_freq: 20000配置文件2：SAC算法
亲测这种算法在高墙时无法收敛，没办法利用方块。且效果比PPO差，平均得分-1。
behaviors:BigWallJump:trainer_type: sachyperparameters:learning_rate: 0.0003learning_rate_schedule: constantbatch_size: 128buffer_size: 200000buffer_init_steps: 0tau: 0.005steps_per_update: 20.0save_replay_buffer: falseinit_entcoef: 0.1reward_signal_steps_per_update: 10.0network_settings:normalize: falsehidden_units: 256num_layers: 2vis_encode_type: simplereward_signals:extrinsic:gamma: 0.99strength: 1.0keep_checkpoints: 5max_steps: 15000000time_horizon: 128summary_freq: 20000SmallWallJump:trainer_type: sachyperparameters:learning_rate: 0.0003learning_rate_schedule: constantbatch_size: 128buffer_size: 50000buffer_init_steps: 0tau: 0.005steps_per_update: 20.0save_replay_buffer: falseinit_entcoef: 0.1reward_signal_steps_per_update: 10.0network_settings:normalize: falsehidden_units: 256num_layers: 2vis_encode_type: simplereward_signals:extrinsic:gamma: 0.99strength: 1.0keep_checkpoints: 5max_steps: 5000000time_horizon: 128summary_freq: 20000配置文件3：
接下来就是课程学习（Curriculum Learning）
behaviors:BigWallJump:trainer_type: ppohyperparameters:batch_size: 128buffer_size: 2048learning_rate: 0.0003beta: 0.005epsilon: 0.2lambd: 0.95num_epoch: 3learning_rate_schedule: linearnetwork_settings:normalize: falsehidden_units: 256num_layers: 2vis_encode_type: simplereward_signals:extrinsic:gamma: 0.99strength: 1.0keep_checkpoints: 5max_steps: 20000000time_horizon: 128summary_freq: 20000SmallWallJump:trainer_type: ppohyperparameters:batch_size: 128buffer_size: 2048learning_rate: 0.0003beta: 0.005epsilon: 0.2lambd: 0.95num_epoch: 3learning_rate_schedule: linearnetwork_settings:normalize: falsehidden_units: 256num_layers: 2vis_encode_type: simplereward_signals:extrinsic:gamma: 0.99strength: 1.0keep_checkpoints: 5max_steps: 5000000time_horizon: 128summary_freq: 20000
environment_parameters:big_wall_height:curriculum:- name: Lesson0 # The '-' is important as this is a listcompletion_criteria:measure: progressbehavior: BigWallJumpsignal_smoothing: truemin_lesson_length: 100threshold: 0.1value:sampler_type: uniformsampler_parameters:min_value: 0.0max_value: 4.0- name: Lesson1 # This is the start of the second lessoncompletion_criteria:measure: progressbehavior: BigWallJumpsignal_smoothing: truemin_lesson_length: 100threshold: 0.3value:sampler_type: uniformsampler_parameters:min_value: 4.0max_value: 7.0- name: Lesson2completion_criteria:measure: progressbehavior: BigWallJumpsignal_smoothing: truemin_lesson_length: 100threshold: 0.5value:sampler_type: uniformsampler_parameters:min_value: 6.0max_value: 8.0- name: Lesson3value: 8.0small_wall_height:curriculum:- name: Lesson0completion_criteria:measure: progressbehavior: SmallWallJumpsignal_smoothing: truemin_lesson_length: 100threshold: 0.1value: 1.5- name: Lesson1completion_criteria:measure: progressbehavior: SmallWallJumpsignal_smoothing: truemin_lesson_length: 100threshold: 0.3value: 2.0- name: Lesson2completion_criteria:measure: progressbehavior: SmallWallJumpsignal_smoothing: truemin_lesson_length: 100threshold: 0.5value: 2.5- name: Lesson3value: 4.0可以看到前半部分和普通的PPO没有区别，区别在environment_parameters:之后，这里定义了课程学习的参数。
课程学习的原理是循序渐进，当一项任务很难的情况下，人们往往会定下一个个小目标，慢慢提升自己，如果想要一下子反而不太现实，就像前面的算法无法达成目标一样。因此在这个任务中我们可以让墙体慢慢升高来达到训练目的。
对于两个网络，我们都把其分为四个训练过程，Lesson0，Lesson1，Lesson2，Lesson3，Lesson4。
其中的参数含义为：
- measure：衡量课程进度的方法。其中的值为reward指的是用奖励衡量，progress指的是用steps/max_steps比例来衡量。
- threshold：配合measure使用，到达这个值时会自动转向课程的下一个阶段。
- min_lesson_length：在转换阶段之前，需要完成的episode的最低数量。
- signal_smoothing：是否通过以前的值来衡量当前的进度（进行加权）。
- 我们可以对每个阶段设定不同的值value，value可以是变化的，sampler_type是采样类型，min_value是采样的最小值，max_value是采样的最大值，sampler_type为uniform在最大值和最小值间均匀采用，为Gaussian是采用正态分布采样。
老版配置方式：
BigWallJump:measure: progressthresholds: [0.1, 0.3, 0.5]min_lesson_length: 100signal_smoothing: trueparameters:big_wall_min_height: [0.0, 4.0, 6.0, 8.0]big_wall_max_height: [4.0, 7.0, 8.0, 8.0]SmallWallJump:measure: progressthresholds: [0.1, 0.3, 0.5]min_lesson_length: 100signal_smoothing: trueparameters:small_wall_height: [1.5, 2.0, 2.5, 4.0]
亲测这种算法最终平均得分0.7，存在少量完不成任务的情况，但效果比上面两种要好得多，可以再对课程进行细分来提高得分。
训练命令：
mlagents-learn config/ppo/WallJump.yaml --run-id=WallJump --force
效果演示
总结
相对于以前的案例，这个案例的新颖之处在于：
- 跳跃的控制，设定了两个触地判定，在下落时给加速度（我的预想是跳跃时给一个向上速度，然后交给物理引擎）
- 多模型训练，设定三种模型，对应三种情况，学习了ModelOverride脚本的使用。
- 探索了课程学习（Curriculum Learning）对训练的影响，学习对应的文件配置。
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