直接使用BezierBy，BezierTo,运动不是匀速的，经过各种搜索之后
在cocos2d\cocos\2d下添加BezeLength.h 和BezeLength.CPP
代码如下
BezeLength.h
double beze_length(double t, float xa, float xb, float xc, float xd, float ya, float yb, float yc, float yd);
double beze_even(double t, double total_length, float xa, float xb, float xc, float xd, float ya, float yb, float yc, float yd);
```
BezeLength.CPP
#include
#include "BezeLength.h"
//x坐标速度方程-------------------------------------------------------------------------------------
double beze_speed_x(double t, float xa, float xb, float xc, float xd)
{
double it = 1-t;
return -3*xa*it*it + 3*xb*it*it - 6*xb*it*t + 6*xc*it*t - 3*xc*t*t + 3*xd*t*t;
}
//y坐标速度方程-------------------------------------------------------------------------------------
double beze_speed_y(double t, float ya, float yb, float yc, float yd)
{
double it = 1-t;
return -3*ya*it*it + 3*yb*it*it - 6*yb*it*t + 6*yc*it*t - 3*yc*t*t + 3*yd*t*t;
}
//速度方程-------------------------------------------------------------------------------------
double beze_speed(double t, float xa, float xb, float xc, float xd, float ya, float yb, float yc, float yd)
{
double sx = beze_speed_x(t, xa, xb, xc, xd);
double sy = beze_speed_y(t, ya, yb, yc, yd);
return sqrt(sx*sx+sy*sy);
}
//长度方程,使用Simpson积分算法-------------------------------------------------------------------------------------
double beze_length(double t, float xa, float xb, float xc, float xd, float ya, float yb, float yc, float yd)
{
//在总长度范围内，使用simpson算法的分割数
#define TOTAL_SIMPSON_STEP (10000)
//分割份数
int stepCounts = (int)(TOTAL_SIMPSON_STEP*t);
if(stepCounts & 1) stepCounts++; //偶数
if(stepCounts==0) return 0.0;
int halfCounts = stepCounts/2;
double sum1=0.0, sum2=0.0;
double dStep = t/stepCounts;
for(int i=0; i<halfCounts; i++)
{
sum1 += beze_speed((2*i+1)*dStep, xa, xb, xc, xd, ya, yb, yc, yd);
}
for(int i=1; i<halfCounts; i++)
{
sum2 += beze_speed((2*i)*dStep, xa, xb, xc, xd, ya, yb, yc, yd);
}
return (beze_speed(0.0, xa, xb, xc, xd, ya, yb, yc, yd)+beze_speed(1.0, xa, xb, xc, xd, ya, yb, yc, yd)+2*sum2+4*sum1)*dStep/3.0;
}
//根据t推导出匀速运动自变量t'的方程(使用牛顿切线法)-------------------------------------------------------------------------------------
double beze_even(double t, double total_length, float xa, float xb, float xc, float xd, float ya, float yb, float yc, float yd)
{
double len = t*total_length; //如果按照匀速增长,此时对应的曲线长度
double t1=t, t2;
do
{
t2 = t1 - (beze_length(t1, xa, xb, xc, xd, ya, yb, yc, yd)-len)/beze_speed(t1, xa, xb, xc, xd, ya, yb, yc, yd);
if(fabs(t1-t2)<0.0000001) break;
t1=t2;
}while(true);
return t2;
}
```
