DirectionalLight

Makes the light effective by setting the appropriate OpenGL state variables. Be sure that the light is on by calling turnOn(), but note that it is on by default.

Shows the light's position in 3D space. This is intended as a debugging aid.

Draws a 3D arrow (comprised of a cylinder and a cone) at the current position specified by the OpenGL modelview matrix, pointing in the direction specified by the vector (xdir, ydir, zdir). This is used for rendering directional lights.

Helps visualize the light's position in 3D space by drawing some lines. This is intended as a debugging aid.