OpenGL如何繪制Bezier曲線

#include<stdlib.h>
#include<stdio.h>
#include<math.h>
#include<GL/glut.h>
//定義控制點數(shù)目的最大值
#define MAX_CPTX 25 
int ncpts=0;//實際控制點個數(shù)
static int width=600,height=600;//窗口大小
typedef struct
{
 GLfloat x,y;
} POINT;
POINT cpts[MAX_CPTX];//存儲控制點坐標(biāo)
//求n!
int JieCheng(int n)
{
 if(n==1||n==0)
 {
 return 1;
 }
 else
 {
 return n*JieCheng(n-1);
 }
}
//求組合排列
double C(int n,int i)
{
 return ((double)JieCheng(n))/((double)(JieCheng(i)*JieCheng(n-i)));
}
//求一個數(shù)u的num次方
double N(double u,int n)
{
 double sum=1.0;
 if (n==0)
 {
 return 1;
 }
 for(int i=0;i<n;i++)
 {
 sum*=u;
 }
 return sum;
}
 
//繪制bezier曲線
void drawBezier(POINT *p)
{ 
 void display();
 if(ncpts<=0) return; 
 
 POINT *p1;
 p1=new POINT[1000];
 GLfloat u=0,x,y;
 int i,num=1;
 p1[0]=p[0];
 for(u=0;u<=1;u=u+0.001)
 { 
 x=0;
 y=0;
 for(i=0;i<ncpts;i++)
 { 
  x+=C(ncpts-1,i)*N(u,i)*N((1-u),(ncpts-1-i))*p[i].x;
  y+=C(ncpts-1,i)*N(u,i)*N((1-u),(ncpts-1-i))*p[i].y;
 }
 p1[num].x=x;
 p1[num].y=y;
 num++;
 } 
 
  glPointSize(4.0);
  glColor3f(0.0,0.0,0.0);
  glBegin(GL_LINE_STRIP);
  for(int k=0;k<1000;k++)
 glVertex2f(p1[k].x,p1[k].y);
  glEnd();
  glFlush();
 return;
}
 
 
 
//輸入新的控制點
static void mouse(int button, int state,int x,int y)
{
void display();
float wx,wy;
//鼠標(biāo)未按下左鍵，不做響應(yīng)
if(state!=GLUT_DOWN)
 return;
else 
 {if(button==GLUT_LEFT_BUTTON)
 {
//轉(zhuǎn)換坐標(biāo)
wx=(2.0*x)/(float)(width-1)-1.0;
wy=(2.0*(height-1-y))/(float)(height-1)-1.0;
//判斷控制點數(shù)目是否超過最大值
if(ncpts==MAX_CPTX)
 return;
//存儲控制點
cpts[ncpts].x=wx;
cpts[ncpts].y=wy;
ncpts++;
//繪制控制點
glColor3f(0.0,0.0,0.0);
glPointSize(5.0);
glBegin(GL_POINTS);
glVertex2f(wx,wy);
glEnd();
glFlush();
}
if(button==GLUT_RIGHT_BUTTON)
{
display();
drawBezier(cpts);
}
}
}
void display(void)
{
 int i;
 glClear(GL_COLOR_BUFFER_BIT);
 glColor3f(0.0,0.0,0.0);
 glPointSize(5.0);
 glBegin(GL_POINTS);
 for (i = 0; i < ncpts; i++)
  glVertex2f(cpts[i].x,cpts[i].y);
 glEnd();
 glFlush();
 
}
//鍵盤回調(diào)函數(shù)
void keyboard(unsigned char key,int x,int y)
{
 switch (key)
 {
  case 'q': case 'Q':
   exit(0);
   break;
  case 'c': case 'C':
 ncpts = 0;
 glutPostRedisplay();
   break;
 case 'r': case 'R':
 ncpts--;
 glutPostRedisplay();
 break;
 }
}
 
//重繪函數(shù)
void reshape(int w,int h)
{
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-1.0,1.0,-1.0,1.0,-1.0,1.0);
glMatrixMode(GL_MODELVIEW);
glViewport(0,0,w,h);//調(diào)整視口
width=w;
height=h;
}
int main(int argc, char **argv)
{
//初始化
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_RGB);
glutInitWindowSize(width,height);
glutCreateWindow("zjc2012211763");
//注冊回調(diào)函數(shù)
glutDisplayFunc(display);
glutMouseFunc(mouse);
glutKeyboardFunc(keyboard);
glutReshapeFunc(reshape);
glClearColor(1.0,1.0,1.0,1.0);
glColor3f(0.0,0.0,0.0);
glutMainLoop();
}