openGL画直线、圆、椭圆

/* args to glViewport are left, bottom, width, height */
glViewport(0, 0, 500, 500);
/* NB: default viewport has same coords as in myinit, */
/* so this could be omitted: */
{
if(d2<=0)
{
d2+=b*b*(2*x+2)+a*a*(-2*y+3);
x++;
y--;
}
else
{
d2+=a*a*(-2*y+3);
y--;
}
putpixel(xc,yc,x,y);
putpixel(xc,yc,-x,-y);
putpixel(xc,yc,-x,y);
putpixel(xc,yc,x,-y);
{
x+=delta_x;
y+=delta_y;
glBegin(GL_POINTS);
glVertex3f(x,y,0);
glEnd();
}
}
/* the display callback: */
void display1() //画圆
{
glClear(GL_COLOR_BUFFER_BIT); /*clear the window */
cout<<"**** 3.用Bresenham算法画椭圆*****"<<endl;
cout<<"************************************************"<<endl;
cout<<"请选择如下操作:";
int choice;
cin>>choice;
switch(choice)
x++;
y--;
}
putpixel(xc,yc,x,y);
putpixel(xc,yc,-x,-y);
putpixel(xc,yc,-x,y);
putpixel(xc,yc,x,-y);
}
d2=b*b*(x+0.5)*(x+0.5)+a*a*(y-1)*(y-1)-a*a*b*b;
while(y>0)
putpixel(xc,yc,-x,-y);
putpixel(xc,yc,-x,y);
putpixel(xc,yc,x,-y);
while(b*b*(x+1)<a*a*(y-0.5))
{
if(d1<0)
{
d1+=b*b*(2*x+3);
x++;
}
else
{
d1+=b*b*(2*x+3)+a*a*(-2*y+2);
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);
{
case 1:
glutCreateWindow("Bresenham circile"); /* window title */
glutDisplayFunc(display1); /* display callback invoked when window opened */
myinit(); /* set attributes */
{
glBegin(GL_POINTS);
glVertex3f(xc+x,yc+y,0);
glVertex3f(xc-x,yc+y,0);
glVertex3f(x(xc-x,yc-y,0);
glVertex3f(xc+y,yc+x,0);
glVertex3f(xc-y,yc+x,0);
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 */
myinit(); /* set attributes */
glutMainLoop(); /* enter event loop */
break;
case 3:
glutCreateWindow("MidBresenhamEllipse"); /* window title */
glutDisplayFunc(display3); /* display callback invoked when window opened */
/* so this could be omitted: */
drawEllipse(250,250,60,40);
/* and flush that buffer to the screen */
glFlush();
}
int main(int argc, char** argv)
{
/* Standard GLUT initialization */
glFlush();
}
void display3() //画圆
{
glClear(GL_COLOR_BUFFER_BIT); /*clear the window */
/*----------------------------------------*/
/* viewport stuff */
/*----------------------------------------*/
glutInit(&argc,argv);
glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); /* default, not needed */
glutInitWindowSize(500,500); /* 500 x 500 pixel window */
glutInitWindowPosition(0,0); /* place window top left on display */
myinit(); /* set attributes */
glutMainLoop(); /* enter event loop */
default: return 0;
}
return 0;
}
glViewport(0, 0, 500, 500);
/* NB: default viewport has same coords as in myinit, */
/* so this could be omitted: */
drawcircle(250,250,100);
/* and flush that buffer to the screen */
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
cout<<"************************************************"<<endl;
cout<<"****请选择如下操作: *****"<<endl;
cout<<"**** 1.用DDA画线*****"<<endl;
cout<<"**** 2.用Bresenham算法画圆*****"<<endl;
glutMainLoop(); /* enter event loop */
break;
case 2:
glutCreateWindow("Digital Differential Analyser Line"); /* window title */
glutDisplayFunc(display2); /* display callback invoked when window opened */
/*----------------------------------------*/
/* viewport stuff */
/*----------------------------------------*/
/* set up a viewport in the screen window */
dda_line(20,20,420,350);
/* and flush that buffer to the screen */
glFlush();
}
void display2() //画圆
{
glClear(GL_COLOR_BUFFER_BIT); /*clear the window */