openGL画直线、圆、椭圆

使用openGl画直线（DDA算法）、画圆、椭圆（Bresenham算法）

#include<stdlib.h>

#include<iostream.h>

#include <GL/glut.h>

/* initialization: */

void myinit(void)

{

/* attributes */

glClearColor(1.0, 1.0, 1.0, 0.0); /* white background */

glColor3f(1.0, 0.0, 0.0); /* draw in red */

/* set up viewing: */

/* 500 x 500 window with origin lower left */

glMatrixMode(GL_PROJECTION);

glLoadIdentity();

gluOrtho2D(0.0, 500.0, 0.0, 500.0);

glMatrixMode(GL_MODELVIEW);

}

void plot_circle_points(int xc,int yc,int x,int y)//画圆

{

glBegin(GL_POINTS);

glVertex3f(xc+x,yc+y,0);

glVertex3f(xc-x,yc+y,0);

glVertex3f(xc+x,yc-y,0);

glVertex3f(xc-x,yc-y,0);

glVertex3f(xc+y,yc+x,0);

glVertex3f(xc-y,yc+x,0);

glVertex3f(xc+y,yc-x,0);

glVertex3f(xc-y,yc-x,0);

glEnd();

}

void drawcircle(int xc,int yc,int radius)

{

int x,y,p;

x=0;

y=radius;

p=3-2*radius;

glClear(GL_COLOR_BUFFER_BIT);

glBegin(GL_POINTS);