title: how can i rotate my object in opengl
body: <p>i rotate my object, that is a triangle . But my object's center moves. </p>
  
  <pre><code>      //background draw
  DrawScreen();
  glPushMatrix();
  
  glTranslatef(xgotur,ygotur,zgotur);
  glRotatef(derece,0.0,0.0,1.0);
  
        // drawing my object
  glBegin(GL_POLYGON);
      glColor3d(0.2, 0.5, 0.7);
      glVertex2f(-0.1+aralik_bosluk, 0.0+aralik_bosluk);
      glVertex2f(0.0+aralik_bosluk,0.4+aralik_bosluk);
      glVertex2f(0.1+aralik_bosluk, 0.0+aralik_bosluk);
  glEnd();    
        // finish draw
  glPopMatrix();   
  </code></pre>