unity3D：游戏分解之曲线

一提到曲线，很多新手就头疼了，包括我。查了很多资料，终于有个大概的了解。想深入了解曲线原理的，推荐一个链接http://www.cnblogs.com/jay-dong/archive/2012/09/26/2704188.html

之前写了一篇博文《unity3D：游戏分解之角色移动和相机跟随》，里面用到了曲线插值，这里算是对上篇博文的一个补充

先看一下曲线的效果

在使用NGUI的过程中，发现iTween.cs里面有两个很有用的方法，一个是输入指定路点数组，一个就是曲线的插值算法。今天我们主要就用到这两个方法来实现曲线效果。

 public static Vector3[] PathControlPointGenerator(Vector3[] path)
     {
         Vector3[] suppliedPath;
         Vector3[] vector3s;

         //create and store path points:
         suppliedPath = path;

         //populate calculate path;
         int offset = ;
         vector3s = new Vector3[suppliedPath.Length + offset];
         Array.Copy(suppliedPath, , vector3s, , suppliedPath.Length);

         //populate start and end control points:
         //vector3s[0] = vector3s[1] - vector3s[2];
         vector3s[] = vector3s[] + (vector3s[] - vector3s[]);
         vector3s[vector3s.Length - ] = vector3s[vector3s.Length - ] + (vector3s[vector3s.Length - ] - vector3s[vector3s.Length - ]);

         //is this a closed, continuous loop? yes? well then so let's make a continuous Catmull-Rom spline!
         if (vector3s[] == vector3s[vector3s.Length - ])
         {
             Vector3[] tmpLoopSpline = new Vector3[vector3s.Length];
             Array.Copy(vector3s, tmpLoopSpline, vector3s.Length);
             tmpLoopSpline[] = tmpLoopSpline[tmpLoopSpline.Length - ];
             tmpLoopSpline[tmpLoopSpline.Length - ] = tmpLoopSpline[];
             vector3s = new Vector3[tmpLoopSpline.Length];
             Array.Copy(tmpLoopSpline, vector3s, tmpLoopSpline.Length);
         }

         return (vector3s);
     }

     //andeeee from the Unity forum's steller Catmull-Rom class ( http://forum.unity3d.com/viewtopic.php?p=218400#218400 ):
     public static Vector3 Interp(Vector3[] pts, float t)
     {
         int numSections = pts.Length - ;
         int currPt = Mathf.Min(Mathf.FloorToInt(t * (float)numSections), numSections - );
         float u = t * (float)numSections - (float)currPt;

         if(currPt == )
         {
             int dsd = ;
         }

         Vector3 a = pts[currPt];
         Vector3 b = pts[currPt + ];
         Vector3 c = pts[currPt + ];
         Vector3 d = pts[currPt + ];

         return .5f * (
             (-a + 3f * b - 3f * c + d) * (u * u * u)
             + (2f * a - 5f * b + 4f * c - d) * (u * u)
             + (-a + c) * u
             + 2f * b
         );
     }

直接上完整代码，把这个脚本放到相机上，然后在场景中拖几个物件作为路点，就可以实现上面的效果

 using System;
 using System.Collections.Generic;
 using UnityEngine;

 namespace Fish.Study.Curve
 {
     /// <summary>
     /// 曲线测试
     /// </summary>
     public class CurveTest : MonoBehaviour
     {
         //路点
         public GameObject[] GameObjectList;
         //各路点的坐标
         public List<Vector3> TransDataList = new List<Vector3>();

         void Start()
         {
         }

         //Gizmos
         void OnDrawGizmos()
         {
             //1个点是不能画出曲线的，2个点实际上是直线
             if (GameObjectList.Length <= ) return;

             TransDataList.Clear();
             for (int i = ; i < GameObjectList.Length; ++i)
             {
                 TransDataList.Add(GameObjectList[i].transform.position);
             }

             if (TransDataList != null && TransDataList.Count > )
             {
                 DrawPathHelper(TransDataList.ToArray(), Color.red);
             }
         }

         public Vector3[] GetCurveData()
         {
             if (TransDataList != null && TransDataList.Count > )
             {
                 var v3 = (TransDataList.ToArray());
                 Vector3[] vector3s = PathControlPointGenerator(v3);
                 return vector3s;
             }

             return null;
         }

         //NGUI iTween.cs中的方法,输入路径点
         public static Vector3[] PathControlPointGenerator(Vector3[] path)
         {
             Vector3[] suppliedPath;
             Vector3[] vector3s;

             //create and store path points:
             suppliedPath = path;

             //populate calculate path;
             int offset = ;
             vector3s = new Vector3[suppliedPath.Length + offset];
             Array.Copy(suppliedPath, , vector3s, , suppliedPath.Length);

             //populate start and end control points:
             vector3s[] = vector3s[] + (vector3s[] - vector3s[]);
             vector3s[vector3s.Length - ] = vector3s[vector3s.Length - ] + (vector3s[vector3s.Length - ] - vector3s[vector3s.Length - ]);

             //is this a closed, continuous loop? yes? well then so let's make a continuous Catmull-Rom spline!
             if (vector3s[] == vector3s[vector3s.Length - ])
             {
                 Vector3[] tmpLoopSpline = new Vector3[vector3s.Length];
                 Array.Copy(vector3s, tmpLoopSpline, vector3s.Length);
                 tmpLoopSpline[] = tmpLoopSpline[tmpLoopSpline.Length - ];
                 tmpLoopSpline[tmpLoopSpline.Length - ] = tmpLoopSpline[];
                 vector3s = new Vector3[tmpLoopSpline.Length];
                 Array.Copy(tmpLoopSpline, vector3s, tmpLoopSpline.Length);
             }

             return (vector3s);
         }

         //曲线插值函数
         public static Vector3 Interp(Vector3[] pts, float t)
         {
             int numSections = pts.Length - ;
             int currPt = Mathf.Min(Mathf.FloorToInt(t * (float)numSections), numSections - );
             float u = t * (float)numSections - (float)currPt;

             Vector3 a = pts[currPt];
             Vector3 b = pts[currPt + ];
             Vector3 c = pts[currPt + ];
             Vector3 d = pts[currPt + ];

             return .5f * (
                 (-a + 3f * b - 3f * c + d) * (u * u * u)
                 + (2f * a - 5f * b + 4f * c - d) * (u * u)
                 + (-a + c) * u
                 + 2f * b
             );
         }

         //画曲线
         private void DrawPathHelper(Vector3[] path, Color color)
         {
             Vector3[] vector3s = PathControlPointGenerator(path);

             //Line Draw:
             Vector3 prevPt = Interp(vector3s, );
             int SmoothAmount = path.Length * ;
             for (int i = ; i <= SmoothAmount; i++)
             {
                 float pm = (float)i / SmoothAmount;
                 Vector3 currPt = Interp(vector3s, pm);

                 Gizmos.color = color;
                 Gizmos.DrawSphere(currPt, 0.2f);
                 prevPt = currPt;
             }
         }
     }
 }