Components of Illumination:

Now consider the light reaching the eye of an observer of a scene:

The light attaining the eye when looking at a surface has obviously come from a source (or sources) of illumination and bounced off the surface. Actually the light reaching the eye may be considered as being built up of 3 different components:

• that from diffuse illumination (incident rays come from all over not just one direction)
• that from a point source that is scattered diffusely from the surface
• that from a point source which is specularly reflected.

We shall consider each of these components separately and then combine them into one.