OpenGL画五角星

#include<GL/glut.h>
#include<math.h>
GLsizei winWidth=400,winHeight=300;//Initial display window size.
#define PI 3.141593
float pCenter[]={200.0,150.0};
float Length=100.0;
float Short=Length*sin(0.1*PI)/sin(0.7*PI);
float p1[]={0.0,0.0},p2[]={0.0,0.0};
void init(void)
{
    glClearColor(1.0,1.0,1.0,0.0);
    glMatrixMode(GL_PROJECTION);
    gluOrtho2D(0,400,0,300);
}
void lineSegment(void)
{
    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f(1.0,0.0,0.0);
            p1[0]=Length+200.0;
            p1[1]=0.0+150.0;

    for(int i=0;i<10;i++)
    {
        if(i%2==0)   //注意不要写成i/2,因为这是取整，我们的是取余
        {
                p2[0]=Short*cos((i+1)*0.2*PI)+pCenter[0];
                p2[1]=Short*sin((i+1)*0.2*PI)+pCenter[1];
        
        }
        else
        {
            p2[0]=Length*cos((i+1)*0.2*PI)+pCenter[0];
            p2[1]=Length*sin((i+1)*0.2*PI)+pCenter[1];
        }
        glBegin(GL_TRIANGLES);
            glVertex2fv(pCenter);
            glVertex2fv(p1);
            glVertex2fv(p2);
        glEnd();
        p1[0]=p2[0];
           p1[1]=p2[1];     
    }

    glFlush();
}    
void main(int argc,char**argv)
{
    
  glutInit(&argc,argv);
  glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
  glutInitWindowPosition(100,200);
  glutInitWindowSize(winWidth,winHeight);
  glutCreateWindow("An Example OpenGL Program");
  init();
  glutDisplayFunc(lineSegment);
  glutMainLoop();

}
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