We use a directional light to illumninate only the sphere. Since two-sided lighting is set to true when we enable the directional light, both the outside and the inside of the sphere will be illuminated by the directional light.

Apart from the light's color (AMBIENT, DIFFUSE and/or SPECULAR), we need only set the light's "position." By setting the fourth component of the position vector to 0.0, the light is directional versus omni or spot. The easiest way to select this light property is to pick a point in world coordinates and use the x, y and z coordinates of the point as the first three components of the position vector. The rays of the directional light will be parallel to the vector that goes from the selected point to the origin.