Simplifying Assumptions of wire frame representation
Neglect colour - consider Intensity: For now we shall forget about colour and restrict our discussion just to the intensity of light. We shall consider white light where the intensity of all colour components (red, green and blue) is equal. This will give us a monochrome (black and white) picture.
Intensity and the 1/r Effect: Usually a light source is a mixture of diffuse background illumination and one or more point sources of light. For the purpose of this discussion (mainly to simplify the mathematics) we shall assume that the light source we are considering is at a large distance from the scene.