drawing a smooth circle

[swatkdw]

hi. I am new to openGL and would like to draw a smooth circle..
Can anyone hint me ?

Should I use gl.glBegin(GL.GL_LINE_STRIP) and some sine, cosin in it??

thanks

[scratt]

Something like this..

const float DEG2RAD = 3.14159/180;
 
void drawCircle(float radius)
{
   glBegin(GL_LINE_LOOP);
 
   for (int i=0; i < 360; i++)
   {
      float degInRad = i*DEG2RAD;
      glVertex2f(cos(degInRad)*radius,sin(degInRad)*radius);
   }
 
   glEnd();
}

Do remember that Google is your friend.. You could have found this with less typing and got a quicker answer with a Google search.

[awhig]

Other solution can be to fake a circle by using gluDisk() and set parameters accordingly. i.e set inner radius equal to outer radius.

Another method can be to go for subdivision curves , midpoint , catmull clark if you want to go for higher precision.

Or you can draw it using NURBS.

You can not get a perfect circle though.

[remdul]

And if you want it to be really really smooth, check out GL_LINE_SMOOTH (hint: enable blending).

[swatkdw]

thank you very much .
I have done it.

gl.glBegin(GL.GL_LINE_LOOP);
for(int i =0; i <= 300; i++){
double angle = 2 * Math.PI * i / 300;
double x = Math.cos(angle);
double y = Math.sin(angle);
gl.glVertex2d(x,y);
}
gl.glEnd();

[MarkS]

Check out this site: http://slabode.exofire.net/circle_draw.shtml

The code there draws circles and arcs without using sine or cosine and is very fast.