RootMotionComputer 根运动计算机

using UnityEngine;
using System.Collections;

/*
 * ----------------------------------------------------------------------------
 * Creation Info
 * ----------------------------------------------------------------------------
 * Root Motion Computer
 * Version: 1.2
 * Date: 2010.12.08
 * Author: Adam Mechtley (http://adammechtley.com)
 * Created for Mixamo, Inc. (http://mixamo.com)
 *
 * ----------------------------------------------------------------------------
 * Description:
 * ----------------------------------------------------------------------------
 * Like many other game engines, Unity was developed with the intent that
 * character animations be created in-place, as though the characters were
 * moving and acting on a treadmill, and the characters‘ root nodes would then
 * be moved programmatically using physics, a character controller, or another
 * procedural mechanism. Unfortunately, many character movements, such as a
 * zombie lurching forward, do not move forward with a constant velocity.
 * Consequently, such motions can introduce foot sliding or dramatic bobbing
 * back and forth when moved procedurally.
 *
 * The Root Motion Computer was designed to solve this problem, particularly by
 * leveraging the fact that motion-capture animations actually capture a moving
 * actor rather than an actor performing in place. Using all of the default
 * settings, the root motion computer uses the movement of the character‘s
 * pelvis to move move the root node. Thus, in-place motions will play back in-
 * place, while motions captured with forward or sideways movement will
 * actually move the character when looping, rather than snapping back to the
 * starting location. Users can also configure the computer‘s various settings
 * to instead pipe its output to another script to drive the velocity of a
 * character controller or another movement tool.
 *
 * ----------------------------------------------------------------------------
 * Usage:
 * ----------------------------------------------------------------------------
 * You can place this script anywhere in your project folder. Because it is
 * written in C#, however, you must put it in your Plugins folder in your
 * project if you are coding in UnityScript.
 *
 * In many cases, you can simply add the component to your character and it
 * should "just work." Otherwise you can manually specify various properties:
 *
 * isManagedExternally: Specifies that another script will invoke Initialize()
 *     and ComputeRootMotion(). This is used if you need to manage the
 *     execution order to prevent the computer from interfering with animation
 *     requests you may make in your own Start(), Awake(), or LateUpdate()
 *     functions.
 * rootNode: The transform that is actually moved, whether by the computer or
 *     by another mechanism like a character controller.
 * anim: The animation component from which to process AnimationStates.
 * pelvis: The character‘s pelvis transform. This object is used to determine
 *     changes in the character‘s overall position or rotation.
 * pelvisForwardAxis: The axis on the pelvis that points to the character‘s
 *     front in the bind pose.
 * pelvisRightAxis: The axis on the pelvis that points to the character‘s right
 *     in the bind pose.
 * computationMode: Specifies whether the computer should compute only forward
 *     translation, all translation (forward-back and side-to-side), or all
 *     translation as well as turning rotation.
 * applyMotion: Specifies whether the computation results should be applied to
 *     rootNode. Set to false if output is going to be read and processed by
 *     another script to move a character controller, for example.
 * deltaPosition: Represents the character‘s change in translation since the
 *     last frame, given in the space of rootNode.
 * deltaRotation: Represents the character‘s change in orientation since the
 *     last frame, given in the space of rootNode.
 * deltaEulerAngles: Same as deltaRotation but converted into Euler angles.
 * isDebugMode: Renders pelvis axes in the scene view when the character is
 *     selected. Renders axis tripods to illustrate the position and
 *     orientation of the pelvis and root node when the game is playing.
 * debugGizmoSize: A scalar for the debug gizmos.
 *
 * ----------------------------------------------------------------------------
 * Notes and Limitations:
 * ----------------------------------------------------------------------------
 * 1. The computer is currently only designed to handle movement of characters
 * forward-back and side-to-side with rotation about their up-axes. As such, it
 * offers no generalized mechanism for adjusting the height of a character
 * (e.g. jumping, going up stairs). Because the computer operates using delta
 * values in LateUpdate(), however, you can implement your own custom logic for
 * adjusting a character‘s height in your own movement code and the computer
 * will simply work on top if it.
 *
 * 2. As of Unity 2.x, there is no way to query the post-normalized weights of
 * AnimationStates. The computer attempts to work around this by rebuilding
 * normalized weights for each state using the same process that Unity uses
 * (applying weights to top-most layers first, and then working down).
 *
 * 3. The computer currently assumes that the clip for any particular
 * AnimationState will not change. (Generally speaking, it should not once it
 * has been added to the animation component anyway.)
 *
 * 4. The computer should support adding new clips at run-time, though the
 * feature has been tested only briefly.
 *
 * 5. Because of how rotation computation works, if a character is on his
 * stomach and then rolls onto his back (or vice-versa), then it is inadvisable
 * to blend in other motions at the time the actual roll occurs (unless it is
 * another synchronized rolling motion).
 * */

// a struct to store information about all of the animation states
/// <summary>
/// 存放动画状态的结构体
/// </summary>
public struct AnimInfo
{

    /// <summary>
    /// 当前动作的规范化时间，直接指向对应动画的规范化时间
    /// </summary>
    public float currentNormalizedTime;
    /// <summary>
    /// 之前动作的规范化时间
    /// </summary>
    public float previousNormalizedTime;
    /// <summary>
    /// 当前动作的权重，直接指向对应动画的权重
    /// </summary>
    public float currentWeight; // the actual weight value queried from the AnimationState
    /// <summary>
    /// 实际播放出来的权重
    /// </summary>
    public float contributingWeight; // the weight the AnimationState is actually contributing to the final result based on layers
    /// <summary>
    /// 当前位置
    /// </summary>
    public Vector3 currentPosition;
    /// <summary>
    /// 之前的位置
    /// </summary>
    public Vector3 previousPosition;
    /// <summary>
    /// 开始位置
    /// </summary>
    public Vector3 startPosition;
    /// <summary>
    /// 结束位置
    /// </summary>
    public Vector3 endPosition;
    /// <summary>
    /// 当前的轴
    /// </summary>
    public Vector3 currentAxis;
    /// <summary>
    /// 之前的轴
    /// </summary>
    public Vector3 previousAxis;
    /// <summary>
    /// 开始的轴
    /// </summary>
    public Vector3 startAxis;
    /// <summary>
    /// 结束的轴
    /// </summary>
    public Vector3 endAxis;
    /// <summary>
    /// 全部旋转
    /// </summary>
    public Quaternion totalRotation;
}

// an enum to describe how delta values should be computed
/// <summary>
/// 增量值计算枚举
/// </summary>
public enum RootMotionComputationMode
{
    ZTranslation,
    XZTranslation,
    TranslationAndRotation
}

/// <summary>
/// 管理所有动画，权重，混合
/// </summary>
[AddComponentMenu("Mixamo/Root Motion Computer")]
public class RootMotionComputer : MonoBehaviour
{
    // the transform to have root motion applied
    /// <summary>
    /// 脚本所在对象
    /// </summary>
    public Transform rootNode;

    // the animation component where all of the clips for this model exist
    /// <summary>
    /// 当前所有的动画数组
    /// </summary>
    public Animation anim;

    // the pelvis joint from which the script obtains x-z motion and y-rotation for the root
    /// <summary>
    /// 模型所在的对象，设置X向Z移动、Y旋转
    /// </summary>
    public Transform pelvis;
    /// <summary>
    /// 骨盆局部的轴，右方向 也是X轴
    /// </summary>
    public Vector3 pelvisRightAxis = Vector3.right; // its local axis specifying the right direction
    /// <summary>
    /// 暂时存储骨盆的局部位置
    /// </summary>
    private Vector3 pLocalPosition; // a variable to temporarily store and set the pelvis local position after computation

    // parameters for computation and application of result
    /// <summary>
    /// 是否是外部管理
    /// </summary>
    public bool isManagedExternally = false; // if the computer is managed externally, then its calls are invoked manually
    /// <summary>
    /// 增量结构
    /// </summary>
    public RootMotionComputationMode computationMode = RootMotionComputationMode.TranslationAndRotation;
    /// <summary>
    /// 应用运动
    /// </summary>
    public bool applyMotion = true;

    // information about the computed root position
    /// <summary>
    /// 来自上一帧的三角州位置
    /// </summary>
    private Vector3 dPosition = Vector3.zero; // local-space delta position since previous frame
    /// <summary>
    /// 来自上一帧的三角州位置
    /// </summary>
    public Vector3 deltaPosition { get { return dPosition; } }
    /// <summary>
    /// 减少分配的一个容器
    /// </summary>
    private Vector3 p; // a simple container to minimize allocations

    // information about the computed root rotation
    /// <summary>
    /// 来自上一帧的三角州旋转
    /// </summary>
    private Quaternion dRotation = Quaternion.identity; // local-space delta rotation since previous frame
    /// <summary>
    /// 来自上一帧的三角州旋转
    /// </summary>
    public Quaternion deltaRotation { get { return dRotation; } }
    /// <summary>
    /// 来自上一帧的三角州旋转的欧拉角
    /// </summary>
    public Vector3 deltaEulerAngles { get { return dRotation.eulerAngles; } }

    // a hashtable storing information about each AnimationState
    /// <summary>
    /// 存放所有动画的哈希表
    /// </summary>
    private Hashtable animInfoTable;
    /// <summary>
    /// 动画状态信息结构体，为了减少分配
    /// </summary>
    private AnimInfo info; // a simple container to minimize allocations

    // specify whether the component should be running in debug mode
    /// <summary>
    /// 是否是调试模式下运行
    /// </summary>
    public bool isDebugMode = true;
    /// <summary>
    /// 调试线框的大小
    /// </summary>
    public float debugGizmoSize = 0.25f;

    // is the computation occuring on the first frame of execution?
    /// <summary>
    /// 计算上的第一帧执行？
    /// </summary>
    private bool isFirstFrame = true;

    // the highest and lowest layers on which there is an AnimationState
    /// <summary>
    /// 最高的层
    /// </summary>
    private int highestLayer = 0;
    /// <summary>
    /// 最低的层
    /// </summary>
    private int lowestLayer = 0;

    /*
     * Initialize the component if it is not managed externally
     * */
    void Start()
    {
        //如果不是外部管理
        if (!isManagedExternally) Initialize();
    }

    /*
     * Initialize all necessary variables and warn user as needed
     * */
    /// <summary>
    /// 必须的初始化
    /// </summary>
    public void Initialize()
    {
        // validate component references
        if (anim == null)
        {
            //取子对象的所有动画
            anim = gameObject.GetComponentInChildren(typeof(Animation)) as Animation;
            if (anim == null) Debug.LogError("No animation component has been specified.", this);
            else if (isDebugMode) Debug.LogWarning(string.Format("No animation component has been specified. Using the animation component on {0}.", gameObject.name), this);
        }
        if (rootNode == null)
        {
            //等于自身
            rootNode = transform;
            if (isDebugMode) Debug.LogWarning(string.Format("No root object has been manually specified. Assuming that {0} is the root object to be moved.", gameObject.name), this);
        }
        if (pelvis == null)
        {
            //取自身的所有组件
            Component[] hierarchy = GetComponentsInChildren(typeof(Transform));
            // first try to figure out the pelvis based on name
            //给骨盆赋值
            foreach (Transform joint in hierarchy)
                if (pelvis == null && (joint.name.ToLower() == "hips" || joint.name.ToLower().Contains("pelvis"))) pelvis = joint;
            // if no named pelvis was found, then try to find the first skinned mesh renderer with children
            if (pelvis == null)
            {
                foreach (Transform joint in hierarchy)
                {
                    if (joint.GetComponent(typeof(SkinnedMeshRenderer)) == null) continue;
                    Component[] children = joint.GetComponentsInChildren(typeof(Transform));
                    if (children.Length > 1) pelvis = joint;
                }
            }
            if (pelvis == null) Debug.LogError("No pelvis transform has been specified.", this);
            else if (isDebugMode) Debug.LogWarning(string.Format("No pelvis object as been manually specified. Assuming that {0} is the pelvis object to track.", pelvis.name));
        }

        // store whether or not the animation component is playing
        bool isAnimationPlaying = anim.isPlaying;

        // store information about each AnimationState in a hashtable for easy lookup later
        animInfoTable = new Hashtable();
        // first, figure out what all AnimationStates are currently doing
        //默认设置给每一个动画
        foreach (AnimationState aState in anim)
        {
            AddAnimInfoToTable(aState);
        }
        //动画采样
        anim.Sample(); // BUG: need to call Sample() once up front or AnimationStates in Animation component may reorder during iteration
        //停止所有动画，以确保所有的动画权重为0
        anim.Stop(); // call Stop() to ensure that all weights go to 0
        //重新启动，以确保采样时的值是正确的
        anim.enabled = true; // reenable the animation component to ensure that values will be correct when sampling
        // store properties for each state one at a time
        foreach (AnimationState aState in anim)
        {
            SetupNewAnimInfo(aState);
        }

        // revert the animation component to whatever it was doing beforehand
        //权重，规范化时间 再次赋值为结构体里面的！当时为何不在设置结构体的时候就直接做了呢？
        foreach (AnimationState aState in anim)
        {
            info = (AnimInfo)animInfoTable[aState];
            //尼玛。这里不是重赋值么
            aState.weight = info.currentWeight;
            aState.normalizedTime = info.currentNormalizedTime;
        }
        if (isAnimationPlaying) anim.Play();
        else anim.Stop();
    }

    /*
     * Add information about the provided state to the hashtable
     * */
    /// <summary>
    /// 设置一个动画的详细信息为结构体，并将之 动画名，结构体 的形式存入哈希表
    /// </summary>
    /// <param name="aState">动画</param>
    public void AddAnimInfoToTable(AnimationState aState)
    {
        // create the new info object
        AnimInfo newInfo = new AnimInfo();

        // store the current properties
        //设置规范化时间
        newInfo.currentNormalizedTime = aState.normalizedTime;
        //设置权重
        newInfo.currentWeight = aState.weight;

        // add a new hashtable entry for the AnimInfo
        //存入动画哈希表中
        animInfoTable.Add(aState, newInfo);
    }

    /*
     * Set up further properties for a newly-created info object after calling AddAnimInfoToTable()
     * */
    /// <summary>
    /// 设置哈希表里动画对应的结构体,重置这个动画
    /// </summary>
    /// <param name="aState">动画名</param>
    public void SetupNewAnimInfo(AnimationState aState)
    {
        //取这个动画的结构体
        AnimInfo newInfo = (AnimInfo)animInfoTable[aState];

        // store information about the animation state up front
        //当前的状态，应当是false 。
        bool isEnabled = aState.enabled;
        WrapMode wrapMode = aState.wrapMode;

        // activate the animation state 激活动画状态
        aState.weight = 1f;
        aState.enabled = true;

        //循环模式 确保该值在normalizedTime=1f是不一定相同normalizedTime= 0F ，官方没有 Clamp 的解释 操
        aState.wrapMode = WrapMode.Clamp; // ensures the value at normalizedTime = 1f is not necessarily the same as normalizedTime = 0f

        // scrub to the beginning of the animation state and store initial position and rotation values
        //净化开始动画状态的初始位置的和旋转值
        aState.normalizedTime = 0f;
        anim.Sample();
        newInfo.startPosition = GetProjectedPosition(pelvis);
        newInfo.previousPosition = GetProjectedPosition(pelvis);
        newInfo.startAxis = GetProjectedAxis(pelvis, pelvisRightAxis);
        newInfo.previousAxis = GetProjectedAxis(pelvis, pelvisRightAxis);

        // scrub to the end of the animation state and store final position and rotation values
        //净化结束的动画状态，并存储最后的位置和旋转值
        aState.normalizedTime = 1f;
        anim.Sample();
        newInfo.endPosition = GetProjectedPosition(pelvis);
        newInfo.endAxis = GetProjectedAxis(pelvis, pelvisRightAxis);

        // store the total rotation over the course of the animation
        //从开始到结束的一个旋转的四元数
        newInfo.totalRotation = Quaternion.FromToRotation(newInfo.startAxis, newInfo.endAxis);

        // reset the clip to its starting point and scrub it down to 0 weight
        //重置这个动画到开始的点到0的权重
        aState.normalizedTime = 0f;
        aState.weight = 0f;
        aState.enabled = isEnabled;
        aState.wrapMode = wrapMode;
        anim.Sample();

        //最后赋值
        animInfoTable[aState] = newInfo;
    }

    /*
     * All motion is applied in LateUpdate() since it is called after all animation states have been set
     * */
    //以保万一才在LatUpdate里运行，因为开头设置了。
    void LateUpdate()
    {
        if (!isManagedExternally) ComputeRootMotion();
    }

    /*
     * Compute the root motion variables
     * */
    /// <summary>
    /// 计算根运动变量
    /// </summary>
    public void ComputeRootMotion()
    {
        // early out if no animation is playing 没运动
        if (!anim.isPlaying) return;

        // store whether or not we should be bothering to compute rotation parameters存储是否我们应该费心去计算旋转参数
        bool isRotationMode = (computationMode == RootMotionComputationMode.TranslationAndRotation);

        #region 设置最高层低层，是否所有的动画都已加入哈希表？没有则添加并设置
        // an array to store any AnimationStates that have been added to the animation component since the last frame
        //一个数组来存储已被添加到自上一帧的动画组件任何AnimationStates，用于初始化没有添加进的动画
        ArrayList newlyAddedAnimationStates = null;

        // first store current actual weight and time information for all AnimationStates
        foreach (AnimationState aState in anim)
        {
            // store the highest and lowest layers for use in a later iteration
            //给最高层和最低层赋值 . 这里每次都要赋一下，让我感到很费解
            highestLayer = Mathf.Max(highestLayer, aState.layer);
            lowestLayer = Mathf.Min(lowestLayer, aState.layer);

            // if any new animation states have been added, then deal with them in a following iteration
            // 这里判断有没有初始化没添加到哈希表的动画
            if (!animInfoTable.ContainsKey(aState))
            {
                AddAnimInfoToTable(aState);
                newlyAddedAnimationStates.Add(aState);
                continue;
            }

            info = (AnimInfo)animInfoTable[aState];
            //我擦。又一次分配
            info.currentNormalizedTime = aState.normalizedTime;
            info.currentWeight = aState.weight;

            animInfoTable[aState] = info;

            // scrub the weight down to 0 for the next iteration
            //为下一次做好准备？？
            aState.weight = 0f;
        }

        // if any new AnimationStates have been added, add their info to the table
        //有新的动画添加，就设置
        if (newlyAddedAnimationStates != null && newlyAddedAnimationStates.Count > 0)
        {
            // first set all weights to 0, which will include newly added states
            foreach (AnimationState aState in anim) aState.weight = 0f;

            // store all the properties for the new states
            foreach (AnimationState aState in newlyAddedAnimationStates) SetupNewAnimInfo(aState);
        }

        #endregion

        #region 计算层的整合，权重的分配。这里有些不懂的地方
        // compute normalized AnimationState weights across layers since Unity does not expose them
        //计算归AnimationState的重量跨越层，因为Unity不暴露他们
        //总的权重，余下的权重
        float remainingWeight = 1f;
        //从最高层开始
        for (int i = highestLayer; i >= lowestLayer; i--)
        {
            //所有动画（指当前的层）权重的总和
            float weightOnThisLayer = 0f;
            //用循环取当前层。layer层中可能有多个动画
            foreach (AnimationState aState in anim)
            {

                if (aState.layer != i) continue;
                //取当前层的当前动画信息
                info = (AnimInfo)animInfoTable[aState];

                // find out how much weight the animation state is actually contributing this frame
                //没有启用动画，或者已分配完
                if (!aState.enabled || remainingWeight <= 0f)
                {
                    info.contributingWeight = 0f;
                }
                else
                {
                    //实际上播放出来的权重
                    info.contributingWeight = remainingWeight * info.currentWeight;
                    //print(aState.name + "-- layer: " + aState.layer  + "还余下的权重：" + remainingWeight + "这个动画当前的权重："
                    //    + info.currentWeight + "实际播放出来的权重" + info.contributingWeight);
                }
                //将这个层上所有的动画的权重加起来
                weightOnThisLayer += info.contributingWeight;
                //print(weightOnThisLayer);
                animInfoTable[aState] = info;
            }
            // if the weight on this layer is > 1, then normalize it
            // using Blend() or setting weights manually will not affect other weights on the layer, so they must be manually renormalized
            //这个层上所有动画权重相加后的数大于1了
            if (weightOnThisLayer > 1f)
            {
                //设置一个百分数来减少实际播放出来的权重
                float oneOverWeightOnThisLayer = 1f / weightOnThisLayer;
                //循环这个层的动画，并做出一些播出的权重的减少
                foreach (AnimationState aState in anim)
                {
                    if (aState.layer != i) continue;
                    info = (AnimInfo)animInfoTable[aState];
                    info.contributingWeight = info.contributingWeight * oneOverWeightOnThisLayer;
                    animInfoTable[aState] = info;
                }
                //重置为1
                weightOnThisLayer = 1f;
            }
            //余下的权重 等于 减去分配后的权重
            remainingWeight -= weightOnThisLayer;
        }

        #endregion

        // reset the delta values for this frame
        //重设此帧的增量值
        dPosition = Vector3.zero;
        dRotation = Quaternion.identity;

        // compute each AnimationState‘s individual contribution to the current frame‘s delta values
        //计算每个动画的贡献，以当前帧的增量值
        foreach (AnimationState aState in anim)
        {
            info = (AnimInfo)animInfoTable[aState];

            // early out if this state was contributing nothing this frame
            //如果没有权重，下一位
            if (info.contributingWeight == 0f) continue;

            // early out if aState uses additive blending
            // NOTE: Not entirely sure if this is ideal or not, but it generally should be
            //如果混合模式为附加，则下一位
            if (aState.blendMode == AnimationBlendMode.Additive) continue;

            // scrub the weight up to 1 for sampling values
            //设置权重为1
            aState.weight = 1f;

            // sample the values for the projected root configuration back one frame
            // NOTE: cannot simply store these values from one frame to the next since user may manually change the time value at any point
            //采样数值为投影机的根目录配置一帧
            //注意：不能简单地存储这些值从一帧到下一个，因为用户可以在任何时候手动更改时间值
            aState.time = aState.time - Time.deltaTime * aState.speed;
            info.previousNormalizedTime = aState.normalizedTime;
            anim.Sample();
            info.previousAxis = GetProjectedAxis(pelvis, pelvisRightAxis);
            info.previousPosition = GetProjectedPosition(pelvis);

            // sample the values for the projected root configuration at the current frame
            aState.normalizedTime = info.currentNormalizedTime;
            anim.Sample();
            info.currentPosition = GetProjectedPosition(pelvis);
            info.currentAxis = GetProjectedAxis(pelvis, pelvisRightAxis);

            // ensure both normalizedTime values are positive
            info.previousNormalizedTime = 1f + info.previousNormalizedTime - (int)info.previousNormalizedTime;
            info.currentNormalizedTime = 1f + info.currentNormalizedTime - (int)info.currentNormalizedTime;

            // determine the contribution to the root‘s delta this frame based on whether the animation looped since the previous frame
            if (info.previousNormalizedTime - (int)info.previousNormalizedTime > info.currentNormalizedTime - (int)info.currentNormalizedTime)
            {
                // compute displacement with respect to identity
                p = info.contributingWeight * ((info.endPosition - info.previousPosition) + (info.currentPosition - info.startPosition));
                if (isRotationMode)
                {
                    // rotate displacement into current orientation
                    p = Quaternion.FromToRotation(info.currentAxis, info.totalRotation * Vector3.right) * p;
                    // compute angular displacement and append to result
                    dRotation *= Quaternion.Slerp(Quaternion.identity,
                        Quaternion.FromToRotation(info.previousAxis, info.endAxis) * Quaternion.FromToRotation(info.startAxis, info.currentAxis),
                        info.contributingWeight);
                }
                // append displacement to result
                dPosition += p;
            }
            else
            {
                // compute displacement with respect to identity
                p = info.contributingWeight * (info.currentPosition - info.previousPosition);
                if (isRotationMode)
                {
                    // rotate displacement into current orientation
                    p = Quaternion.FromToRotation(info.currentAxis, Vector3.right) * p;
                    // compute angular displacement and append to result
                    dRotation *= Quaternion.Slerp(Quaternion.identity, Quaternion.FromToRotation(info.previousAxis, info.currentAxis), info.contributingWeight);
                }
                // append displacement to result
                dPosition += p;
            }

            // scrub the weight back down to 0 so as to not affect sampling of other states
            aState.weight = 0f;
        }

        // reset weights to where they were before computation
        foreach (AnimationState aState in anim)
        {
            info = (AnimInfo)animInfoTable[aState];
            aState.weight = info.currentWeight;
        }

        // return the character to its current pose
        anim.Sample();

        // delta values for the first frame should simply move from the starting configuration into the current frame of animation
        if (isFirstFrame)
        {
            // simply translate and rotate to the current projected position and orientation
            dPosition = GetProjectedPosition(pelvis);
            dRotation = Quaternion.FromToRotation(Vector3.right, GetProjectedAxis(pelvis, pelvisRightAxis));

            // rotate displacement into current orientation
            if (isRotationMode) dPosition = Quaternion.FromToRotation(GetProjectedAxis(pelvis, pelvisRightAxis), Vector3.right) * dPosition;

            isFirstFrame = false;
        }

        // store the local position of the pelvis before returning it to hover over the root
        pLocalPosition = pelvis.localPosition;

        // zero out the local x-component of the position delta if root translation method is z-only
        if (computationMode == RootMotionComputationMode.ZTranslation) dPosition = Vector3.forward * Vector3.Dot(dPosition, Vector3.forward);
        // otherwise zero out the local x-position of the pelvis
        else pLocalPosition.x = 0f;

        // return the pelvis to a point hovering over the root
        pLocalPosition.z = 0f;
        pelvis.localPosition = pLocalPosition;

        // if computing rotation, then zero out local y-rotation of the pelvis
        if (isRotationMode) pelvis.localRotation = Quaternion.FromToRotation(GetProjectedAxis(pelvis, pelvisRightAxis), Vector3.right) * pelvis.localRotation;

        // draw debug lines if requested
        if (isDebugMode) DrawDebug();

        // return if root movement is not requested (e.g. a character controller will use delta values)
        if (!applyMotion) return;

        // apply rotation if requested
        if (isRotationMode) rootNode.localRotation *= dRotation;

        // apply translation
        rootNode.Translate(dPosition, Space.Self);
    }

    /*
     * Obtain the position of t projected onto rootNode‘s zx plane
     * */
    /// <summary>
    /// 获取传入位置投射在根结点的ZX轴坐标的一个点 ，y = 0
    /// </summary>
    /// <param name="t">传入的位置</param>
    /// <returns></returns>
    private Vector3 GetProjectedPosition(Transform t)
    {
        Vector3 p = rootNode.InverseTransformPoint(t.position);
        p.y = 0f;
        return p;
    }

    /*
     * Obtain the projection of axis on t onto rootNode‘s zx plane
     * */
    /// <summary>
    /// 获取根节点的zx平面上的投影轴
    /// </summary>
    /// <param name="t">传入的位置</param>
    /// <param name="axis">方向</param>
    /// <returns></returns>
    private Vector3 GetProjectedAxis(Transform t, Vector3 axis)
    {
        Vector3 p = rootNode.InverseTransformDirection(t.TransformDirection(axis));
        p.y = 0f;
        return p;
    }

    /*
     * Draw axis tripods to show how root motion is being determined and applied
     * */
    private void DrawDebug()
    {
        // draw pelvis right axis
        Debug.DrawRay(pelvis.position, pelvis.TransformDirection(pelvisRightAxis) * debugGizmoSize, Color.red);

        // draw root node axes
        Debug.DrawRay(rootNode.position, rootNode.rotation * Vector3.forward * debugGizmoSize, Color.blue);
        Debug.DrawRay(rootNode.position, rootNode.rotation * Vector3.right * debugGizmoSize, Color.red);
        Debug.DrawRay(rootNode.position, rootNode.rotation * Vector3.up * debugGizmoSize, Color.green);
    }
}