路径控制器

控制一个GameObject随着某一个路径进行移动，这是一个经常需要用到的功能。一个比较常用的实现方式是利用DoTween这样的插件来做到，其他的方式也都大同小异，原理都是通过设置一条路径，然后每一帧都利用这个路径来计算当前需要出现的位置，然后把目标GameObject放到那个位置上。

那这里我就对这种方式进行一个封装，写一个类来专门做这件事，这样以后每次需要用这个功能的时候就只要一行代码就可以实现。原理很简单，代码也不复杂。

using UnityEngine;
using System.Collections.Generic;


namespace LDFW.Math
{

    [System.Serializable]
    public class LDFWPath
    {

        public AnimationCurve xValueCurve;
        public AnimationCurve yValueCurve;
        public AnimationCurve zValueCurve;

        public float totalDistance;
        public bool useSmoothCurve = true;

        public LDFWPath()
        {
            Init();
        }

        public void Init()
        {
            xValueCurve = new AnimationCurve();
            yValueCurve = new AnimationCurve();
            zValueCurve = new AnimationCurve();
            totalDistance = 0;
        }


        public void ConstructPath(Vector3[] pathPoints)
        {
            if (pathPoints == null || pathPoints.Length < 2)
            {
                return;
            }
            Init();

            float[] pathDistance = new float[pathPoints.Length];
            totalDistance = 0;
            pathDistance[0] = 0;
            for (int i = 1; i < pathPoints.Length; i++)
            {
                totalDistance += Vector3.Distance(pathPoints[i], pathPoints[i - 1]);
                pathDistance[i] = totalDistance;
            }


            float currentDistance = 0;
            float currentPercentage = 0;
            Vector3 inTangent = Vector3.zero;
            Vector3 outTangent = Vector3.zero;

            // Add first point
            if (useSmoothCurve)
                AddSmoothKeyFrame(pathPoints[0], 0);
            else
            {
                float deltaPercentage = pathDistance[1] / totalDistance;
                if (deltaPercentage == 0)
                    AddSmoothKeyFrame(pathPoints[0], 0);
                else
                    AddTangentKeyFrame(pathPoints[0], 0, Vector3.zero, (pathPoints[1] - pathPoints[0]) / (pathDistance[1] / totalDistance));
            }

            // Add rest points
            for (int i = 1; i < pathPoints.Length; i++)
            {
                currentDistance += Vector3.Distance(pathPoints[i], pathPoints[i - 1]);
                currentPercentage = currentDistance / totalDistance;

                if (useSmoothCurve)
                {
                    AddSmoothKeyFrame(pathPoints[i], currentPercentage);
                }
                else
                {
                    if (i == pathPoints.Length - 1)
                    {
                        inTangent = (pathPoints[i] - pathPoints[i - 1]) / ((pathDistance[i] - pathDistance[i - 1]) / totalDistance);
                        outTangent = Vector3.zero;
                    }
                    else
                    {
                        inTangent = (pathPoints[i] - pathPoints[i - 1]) / ((pathDistance[i] - pathDistance[i - 1]) / totalDistance);
                        outTangent = (pathPoints[i + 1] - pathPoints[i]) / ((pathDistance[i + 1] - pathDistance[i]) / totalDistance);
                    }
                    AddTangentKeyFrame(pathPoints[i], currentPercentage, inTangent, outTangent);
                }
            }
        }

        public void ConstructPath(List<Vector3> pointList)
        {
            for (int i = 1; i < pointList.Count; i++)
            {
                if (pointList[i] == pointList[i - 1])
                {
                    pointList.RemoveAt(i);
                    i--;
                }
            }

            ConstructPath(pointList.ToArray());
        }


        public void AddSmoothKeyFrame(Vector3 position, float percentage)
        {
            percentage = Mathf.Clamp(percentage, 0, 1);

            int x = xValueCurve.AddKey(percentage, position.x);
            int y = yValueCurve.AddKey(percentage, position.y);
            int z = zValueCurve.AddKey(percentage, position.z);
        }

        public void AddTangentKeyFrame(Vector3 position, float percentage, Vector3 inTangent, Vector3 outTangent)
        {
            percentage = Mathf.Clamp(percentage, 0, 1);

            int x = xValueCurve.AddKey(new Keyframe(percentage, position.x, inTangent.x, outTangent.x));
            int y = yValueCurve.AddKey(new Keyframe(percentage, position.y, inTangent.y, outTangent.y));
            int z = zValueCurve.AddKey(new Keyframe(percentage, position.z, inTangent.z, outTangent.z));
        }

        public Vector3 Evaluate(float percentage)
        {
            return new Vector3(xValueCurve.Evaluate(percentage), yValueCurve.Evaluate(percentage), zValueCurve.Evaluate(percentage));
        }

    }

}