title: handling click on 3d or 2d figure in opengl
body: <p>how to handle clik on specific 3d or 2d object in opengl, for example i have the following code </p>
  
  <pre><code>void Widget::drawCircle(float radius) {
      glBegin(GL_TRIANGLE_FAN);
      for (int i = 0; i &lt; 360; i++) {
          float degInRad = i*DEG2RAD;
          glVertex2f(cos(degInRad) * radius, sin(degInRad) * radius);
      }
      glEnd();
  }
  </code></pre>
  
  <p>So i need to handle click on this circle, is there any solutions for this problem?</p>