openGL画直线、圆、椭圆(2)

while(x<y)

{

plot_circle_points(xc,yc,x,y);

if(p<0)

p=p+4*x+6;

else

{

p=p+4*(x-y)+10;

y-=1;

}

x+=1;

}

if(x==y)

plot_circle_points(xc,yc,x,y);

}

void putpixel(int xc,int yc,int x,int y)//画椭圆

{

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

glEnd();

}

void drawEllipse(int xc,int yc,int a,int b)

{

int x,y;

float d1,d2;

x=0; y=b; d1=b*b+a*a*(-b+0.25); putpixel(xc,yc,x,y); 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) { } else { d1+=b*b*(2*x+3)+a*a*(-2*y+2); d1+=b*b*(2*x+3); x++;