Bresnham algorithm (two) code implementation

Bresnham algorithm (two) code implementation

Code:

#include <GL/glut.h> 
#include<math.h>
#include<iostream>
using namespace std;
float r;
void MidPointCircle(void)
{
    int x, y;
    float d;
    x = 0; y = r; d = 1 - r;
    while (x <= y)
    {
        glBegin(GL_POINTS);
        glColor3f(1.0, 0.0, 0.0);//线的颜色为红色
        glVertex3f(x, y, 0);
        glVertex3f(-x, -y, 0);
        glVertex3f(-x, y, 0);
        glVertex3f(x, -y, 0);
        glVertex3f(y, -x, 0);
        glVertex3f(-y, -x, 0);
        glVertex3f(-y, x, 0);
        glVertex3f(y, x, 0);
        glEnd();
        if (d < 0)
        {
            d += 2 * x + 3;
        }
        else { 
            d += 2 * (x - y) + 5;  
            y--;
        }
        x++;
        
    }
    glFlush();

}
void main(int argc, char** argv) {
    glutInit(&argc, argv); //初始化glut
    glutInitDisplayMode(GLUT_DEPTH | GLUT_SINGLE | GLUT_RGBA);
    //设置窗口的模式－深度缓存，单缓存，颜色模型
    glutInitWindowPosition(200, 200); //设置窗口的位置
    glutInitWindowSize(500, 500); //设置窗口的大小
    glutCreateWindow("3D Tech- GLUT Tutorial"); //创建窗口并赋予title
    cout << "输入r" << endl;
    cin >> r;
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(-500.0, 500.0, -500.0, 500.0);
    glMatrixMode(GL_MODELVIEW);
    glutDisplayFunc(MidPointCircle);//调用renderScene把绘制传送到窗口
    glutMainLoop(); //进入循环等待
}

operation result: