Our primary lighting consists of a directional light that points in the direction parallel to the vector from (1, 0, 1) to the origin. We also add a dark gray ambient light (the color darkGray is defined in RGB.h). The use of ambient light allows us to see, although dimly, those facets not illuminated by our directional light. We enable here the directional light (GL_LIGHT1) but do not enable lighting in general since it is used only when rendering the cylinder if the user selects that option.