opengl使用两条Bezier曲线绘制的平面鸡蛋

#include <GL/glut.h>
#include <GL/glu.h>

float aVertex[4][3]={{-0.5,0,0},{-0.3,0.8,0},{0.3,0.8,0},{0.5,0,0}};
float bVertex[4][3]={{-0.5,0,0},{-0.66,-0.6,0},{0.66,-0.8,0},{0.5,0,0}};

void display()
{
    glClear(GL_COLOR_BUFFER_BIT);
    glColor4f(0.4,0.5,0.7,1);
    glBegin(GL_POINTS);
    glVertex3fv(aVertex[0]);
    glVertex3fv(aVertex[1]);
    glVertex3fv(aVertex[2]);
    glVertex3fv(aVertex[3]);
    glEnd();
    glColor3f(0.7,0.2,0.2);
    glMap1f(GL_MAP1_VERTEX_3,0,1,3,4,&aVertex[0][0]);
    glEnable(GL_MAP1_VERTEX_3);
    glBegin(GL_LINE_STRIP);
    const int NUM=30;
    for(int i=0;i<=NUM;++i)
    {
        glEvalCoord1f(1.0f*i/NUM);
    }
    glEnd();
    glDisable(GL_MAP1_VERTEX_3);
    glMap1f(GL_MAP1_VERTEX_3,0,1,3,4,&bVertex[0][0]);
    glEnable(GL_MAP1_VERTEX_3);
    glBegin(GL_LINE_STRIP);
    for(int i=0;i<=NUM;++i)
    {
        glEvalCoord1f(1.0f*i/NUM);
    }
    glEnd();
    glDisable(GL_MAP1_VERTEX_3);
    glutSwapBuffers();
}

void reshape(int w,int h)
{
    glViewport(0,0,w,h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(120,1,0.1,10);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    gluLookAt(0,0,1,0,0,0,0,1,0);
}

void init()
{
    glClearColor(0,0,0,0);
    glShadeModel(GL_SMOOTH);
}

int main(int argc,char**argv)
{
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGBA);
    glutInitWindowSize(500,500);
    glutInitWindowPosition(0,0);
    glutCreateWindow(argv[0]);
    init();
    glutDisplayFunc(display);
    glutReshapeFunc(reshape);
    glutMainLoop();
    return 0;
}