loading a 3d model (it looks like 2d)

the question is why my model looks like 2d?
I use maya 2008
and exported the model by maya2egg2008 -a model -keep-uvs head.mb -o sphere.egg
also the material is lambert ( i just change to color)



NodePath smiley;
    smiley = window->load_model(framework.get_models(),"/home/alex/NetBeansProjects/sphere.egg");
    smiley.set_pos(0, 0, 0);

You need to have lighting.

can you please explain it