在Opengl应用框架下圆弧的扫描转换算法。

在Opengl应用框架下圆弧的扫描转换算法。要求画一个完整的圆周，圆心在（300，200），半径为50.

#include 
#include 
#include 
#include 
#include 
using namespace std;
#define pi 3.1415926

void init(void){
    glClearColor(1.0, 1.0, 1.0, 0.0);  
    glMatrixMode(GL_PROJECTION);      
    gluOrtho2D(0.0, 600.0, 0.0, 600.0);
}

void ChangeSize(GLsizei w, GLsizei h) {
    if (h == 0)
        h = 1;
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    if (w <= h)
        glOrtho(0.0f, 600.0f, 0.0f, 600.0f * h / w, 1.0, -1.0);
    else
        glOrtho(0.0f, 600.0f * w / h, 0.0f, 600.0f,1.0, -1.0);
}

void CirclePoint(int x0, int y0, int x, int y) {
    glColor3f(0.0, 0.0, 1.0);  
    glVertex2f(x, y); glVertex2f(y - (y0 - x0), x + (y0 - x0));
    glVertex2f(y - (y0 - x0), x0 + y0 - x); glVertex2f(x, 2 * y0 - y);
    glVertex2f(2 * x0 - x, 2 * y0 - y); glVertex2f(x0 + y0 - y, x0 + y0 - x);
    glVertex2f(x0 + y0 - y, x + (y0 - x0)); glVertex2f(2 * x0 - x, y);
}

//中点画圆算法
void MidPointCircle(int x0, int y0, int r){
    glColor3f(0.0, 0.0, 1.0);  
    glPointSize(2.0f);       
    glVertex2f(x0, y0);  //圆心      
    int x, y;
    int d, b;
    x = x0; y = r + y0; d = 5 - 4 * r; b = y0 - x0;
    CirclePoint(x0, y0, x, y);
    while (x + b <= y){
        if (d < 0)
            d += 8 * (x - x0) + 12;
        else {
            d += 8 * x - 8 * y + 8 * b + 16;
            y--;
        }
        x++;
        CirclePoint(x0, y0, x, y);
    } 
}

void display(){
    glClear(GL_COLOR_BUFFER_BIT);
    glBegin(GL_POINTS);
    MidPointCircle(300, 200, 50);
    glEnd();
    glFlush();
}

int main(int argc, char** argv){
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE); 
    glutInitWindowPosition(100, 100);            
    glutInitWindowSize(500, 500);               
    glutCreateWindow("Line Algorithm");           
    glutDisplayFunc(display);                  
    glutReshapeFunc(ChangeSize);
    init();
    glutMainLoop();             
    return 0;
}

运行结果