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标题: 三个点生成抛物线 ，计算组成抛物线的点 [打印本页]
作者: 王者再临    时间: 2015-10-28 00:30
标题: 三个点生成抛物线 ，计算组成抛物线的点
  1. using UnityEngine;
  2. using System.Collections;
  3. using System.Collections.Generic;
  4. //iTween里抄来的
  5. public class otherTest : MonoBehaviour {

  7.         /// <summary>
  8.         /// 三点计算抛物线.
  9.         /// </summary>
  10.         /// <returns>组成抛物线的点.</returns>
  11.         /// <param name="path">确定抛物线的三个点或者更多的点的数组.</param>
  12.         public static List<Vector3> DrawPathHelper(Vector3[] path){
  13.                 List<Vector3> array = new List<Vector3>(177);
  14.                 Vector3[] vector3s = PathControlPointGenerator(path);
  15.                 //Line Draw:
  16.                 Vector3 prevPt = Interp(vector3s,0);
  17.                 int SmoothAmount = path.Length*20;
  18.                 for (int i = 1; i <= SmoothAmount; i++)
  19.                 {
  20.                         float pm = (float) i / SmoothAmount;
  21.                         Vector3 currPt = Interp(vector3s,pm);
  22.                                 array.Add(currPt);
  23.                         prevPt = currPt;
  24.                 }
  25.                 return  array;
  26.         }
  27.        
  28.         private static Vector3[] PathControlPointGenerator(Vector3[] path){
  29.                 Vector3[] suppliedPath;
  30.                 Vector3[] vector3s;
  31.                
  32.                 //create and store path points:
  33.                 suppliedPath = path;
  34.                
  35.                 //populate calculate path;
  36.                 int offset = 2;
  37.                 vector3s = new Vector3[suppliedPath.Length+offset];
  38.                 System.Array.Copy(suppliedPath,0,vector3s,1,suppliedPath.Length);
  39.                
  40.                 //populate start and end control points:
  41.                 //vector3s[0] = vector3s[1] - vector3s[2];
  42.                 vector3s[0] = vector3s[1] + (vector3s[1] - vector3s[2]);
  43.                 vector3s[vector3s.Length-1] = vector3s[vector3s.Length-2] + (vector3s[vector3s.Length-2] - vector3s[vector3s.Length-3]);
  44.                
  45.                 //is this a closed, continuous loop? yes? well then so let's make a continuous Catmull-Rom spline!
  46.                 if(vector3s[1] == vector3s[vector3s.Length-2]){
  47.                         Vector3[] tmpLoopSpline = new Vector3[vector3s.Length];
  48.                         System.Array.Copy(vector3s,tmpLoopSpline,vector3s.Length);
  49.                         tmpLoopSpline[0]=tmpLoopSpline[tmpLoopSpline.Length-3];
  50.                         tmpLoopSpline[tmpLoopSpline.Length-1]=tmpLoopSpline[2];
  51.                         vector3s=new Vector3[tmpLoopSpline.Length];
  52.                         System.Array.Copy(tmpLoopSpline,vector3s,tmpLoopSpline.Length);
  53.                 }       
  54.                
  55.                 return(vector3s);
  56.         }

  58.         //andeeee from the Unity forum's steller Catmull-Rom class ( http://forum.unity3d.com/viewtopic.php?p=218400#218400 ):
  59.         private static Vector3 Interp(Vector3[] pts, float t){
  60.                 int numSections = pts.Length - 3;
  61.                 int currPt = Mathf.Min(Mathf.FloorToInt(t * (float) numSections), numSections - 1);
  62.                 float u = t * (float) numSections - (float) currPt;
  63.                
  64.                 Vector3 a = pts[currPt];
  65.                 Vector3 b = pts[currPt + 1];
  66.                 Vector3 c = pts[currPt + 2];
  67.                 Vector3 d = pts[currPt + 3];
  68.                
  69.                 return .5f * (
  70.                         (-a + 3f * b - 3f * c + d) * (u * u * u)
  71.                         + (2f * a - 5f * b + 4f * c - d) * (u * u)
  72.                         + (-a + c) * u
  73.                         + 2f * b
  74.                         );
  75.         }       
  76. }
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