Polygon Won't Show Up In The Screen
===

I am trying to draw a 6 sided [obelisk][1] using opengl.

Below is the code I use to draw the bottom of the obelisk:

    glColor3f(1.0,1.0,0.0);

    glBegin(GL_POLYGON);
	for ( x=0.0; x<2.0*pi/3; x=x+inc )
	{	
		glVertex3f(0.3*cos(x),0.3*sin(x),0.0);
	}
	glEnd();

For certain reasons the polygon surface that I drew didn't show up on the screen once the model is rendered.

I hope anyone can advise me in this matter, thank you.


  [1]: http://en.wikipedia.org/wiki/Obelisk