OpenGL八对称和内接正多边形逼近画圆法

//void cirpot(int x1, int y1, int x, int y) {
//    glBegin(GL_POINTS);
//    glVertex2i(x1 + x, y1 + y);
//    glVertex2i(x1 - x, y1 + y);
//    glVertex2i(x1 + x, y1 - y);
//    glVertex2i(x1 - x, y1 - y);
//
//    glVertex2i(x1 + y, y1 + x);
//    glVertex2i(x1 -y, y1 + x);
//    glVertex2i(x1 + y, y1 -x);
//    glVertex2i(x1 -y, y1 -x);
//    glEnd();
//    glFlush();
//    Sleep(100);
//}
//void circle_8(int x1, int y1, int r) {              //八对称  ok!!!!!!!!
//    int x, y;
//    for (x = 0; x <= sqrt(2) / 2 * r; x++) {
//        y = (int)sqrt(r * r - x * x);
//        cirpot(x1, y1,x,y);
//    }
//}

//void myDisplay(void) {
//    ///////////////////////////////circle_8(300, 300,100);///////八对称  ok!!!!!!!!
//    //内接正多边形逼近圆
//    int x0 = 250, y0 = 250, r = 100;
//    int i, n = 100;
//    float st;
//    glClear(GL_COLOR_BUFFER_BIT);
//    st = (360.0 / n) * (3.14 / 180);//角度转换为弧度
//    glColor3f(0.0f, 0.0f, 0.0f);
//    glBegin(GL_LINE_LOOP);
//    for (int i = 0; i < n; i++) {
//        glVertex2f(x0 + r * cos(i * st), y0 + r * sin(i * st));
//    }
//    glEnd();
//    glFlush();
//}