This file contains the two functions in gl_canvas.cc that were 
modified to make the "car-world" example program.

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void GLCanvas::createWorld() {

   Model *world = new Model();  // This holds all the objects in the world.

   xRotate = new Rotate(5,1,0,0);  // (Variables defined in gl_canvas.h.)
   yRotate = new Rotate(0,0,1,0);

   world->addTransform(xRotate)  // The rotations affect the entire world.
        ->addTransform(yRotate);
        
   sunRotate = new Rotate(-60,0,0,1);
   moonRotate = new Rotate(-240,0,0,1);
   carRotate = new Rotate(0,0,1,0);
        
   Model *sun = new Model();
   sun->addObject( (new BasicObject(SPHERE))
                          ->setEmissiveColor(0.8,0.8,0));
   sun->addObject( (new Light(0,0,0,1))
                          ->setColor(.8,.8,.6) );
   sun->addTransform( new Translate(-5,0,0) );
   sun->addTransform(sunRotate);
        
   Model *moon = new Model();
   moon->addObject( (new BasicObject(SPHERE))
                          ->addTransform(new Scale(0.6))
                          ->setEmissiveColor(0.5,0.5,0.6));
   moon->addObject( (new Light(0,0,0,1))
                          ->setColor(.3,.3,.4) );
   moon->addTransform( new Translate(-5,0,0) );
   moon->addTransform(moonRotate);
        
   Model *axel = new Model();
   axel->setColor(0,0,1);
   axel->setSpecularColor(0,0,0);
   axel->addObject( (new BasicObject(CYLINDER))
                         ->addTransform(new Scale(0.3,6,0.3))
                         ->addTransform(new Rotate(90,1,0,0)) );
   axel->addObject( (new BasicObject(TORUS))
                         ->addTransform(new Scale(2))
                         ->addTransform(new Translate(0,0,3)) );
   axel->addObject( (new BasicObject(TORUS))
                         ->addTransform(new Scale(2))
                         ->addTransform(new Translate(0,0,-3)) );
                         
   Model *car = new Model();
   car->setSpecularColor(0.2,0.2,0.2);
   car->addObject( new Model(axel,new Translate(5,0,0)) );
   car->addObject( new Model(axel,new Translate(-5,0,0)) );
   car->addObject( (new BasicObject(CUBE)) 
                         ->setColor(1,0,0)
                         ->addTransform(new Scale(12,2,5))
                         ->addTransform(new Translate(0,1,0)) );
   car->addObject( (new BasicObject(CUBE)) 
                         ->setColor(1,0,0)
                         ->addTransform(new Scale(5,2,4.5))
                         ->addTransform(new Translate(1,2,0)) );
   car->addObject( (new BasicObject(SPHERE))
                         ->setColor(1,1,0)
                         ->addTransform(new Scale(0.2,1,1))
                         ->addTransform(new Translate(-6,1,-1.7)) );
   car->addObject( (new BasicObject(SPHERE))
                         ->setColor(1,1,0)
                         ->addTransform(new Scale(0.2,1,1))
                         ->addTransform(new Translate(-6,1,1.7)) );
   car->addTransform(new Scale(0.15))
      ->addTransform(new Translate(0,0.15,-3))
      ->addTransform(carRotate);
 
   Model *tree = new Model();
   tree->setSpecularColor(0,0,0);
   tree->addObject( (new BasicObject(CONE))
                         ->setColor(0.2,0.8,0.3)
                         ->addTransform(new Translate(0,0.5,0))
                         ->addTransform(new Scale(1,1.5,1)) );
   tree->addObject( (new BasicObject(CYLINDER))
                         ->setColor(0.6,0.5,0.2)
                         ->addTransform(new Scale(0.2,1,0.2)) );
   tree->addTransform( new Translate(0,0.5,0) );
                         
   Object *ground = (new BasicObject(CYLINDER))
                         ->setColor(0,0.5,0.2)
                         ->setSpecularColor(0,0,0)
                         ->addTransform( new Scale(8,0.1,8) )
                         ->addTransform( new Translate(0,-0.05,0) );

   world->addObject( sun );
   world->addObject( moon );
   world->addObject( ground );
   world->addObject( car );
   world->addObject( tree );
   world->addObject( (new Model(tree))
                       ->addTransform(new Scale(0.7))
                       ->addTransform(new Translate(1.5,0,1)) );
   world->addObject( (new Model(tree))
                       ->addTransform(new Scale(0.5))
                       ->addTransform(new Translate(-1.8,0,1.2)) );
   world->addObject( (new Model(tree))
                       ->addTransform(new Scale(0.7))
                       ->addTransform(new Translate(0.3,0,-2)) );
   world->addObject( (new Model(tree))
                       ->addTransform(new Scale(0.3))
                       ->addTransform(new Translate(-0.5,0,-1)) );

   float ambient[4] = {0.3,0.3,0.3,1};
   glLightModelfv(GL_LIGHT_MODEL_AMBIENT,ambient);
   
   
   worldview = new View(world);  // Let worldview be a view of the world
                                 // that was just created.
}


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void GLCanvas::timerEvent(QTimerEvent *evt) {
   float angle = sunRotate->getAngle();
   angle -= 3;
   if (angle <= 0)
      angle += 360;
   sunRotate->setAngle(angle);
   moonRotate->setAngle(angle+180);
   updateGL();
   angle = carRotate->getAngle();
   angle += 5;
   if (angle > 360)
      angle -= 360;
   carRotate->setAngle(angle);
}