Q:

fill rectangle and apply nonzero winding rule in opengl

this is simple rectangle drawing code in opengl..i want to fill the rectangle with some color and want to apply non-zero winding rule to tell the user whether rectangle is filled for inside or outside...how can i achieve this???
#include <cstdlib>
#include <iostream>
#include<GL/glut.h>

using namespace std;

#include <GL/glut.h>

void display(void)
{
   glClear (GL_COLOR_BUFFER_BIT);

   glColor3f (1.0, 1.0, 1.0);
   glBegin(GL_POLYGON);
      glVertex3f (0.25, 0.25, 0.0);
      glVertex3f (0.75, 0.25, 0.0);
      glVertex3f (0.75, 0.75, 0.0);
      glVertex3f (0.25, 0.75, 0.0);
   glEnd();

   glFlush ();
}

void init (void) 
{

   glClearColor (0.0, 0.0, 0.0, 0.0);

   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
}

int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
   glutInitWindowSize (250, 250); 
   glutInitWindowPosition (100, 100);
   glutCreateWindow ("hello");
   init ();
   glutDisplayFunc(display); 
   glutMainLoop();
   return 0;  
}

A:

Use the GLU Tesselator.

