Definition 3
The third component of light from a light source is specular light. Ambient light has been scattered from many surfaces and seems to come from all directions. Diffuse light comes from a specific direction (the source, of course), but scatters from surfaces, giving a soft, "flat" appearance to surfaces. Ambient and Diffuse components of a light source commonly share the same color. Specular light is also directional, but much "tighter" in reflection than diffuse light, often with a different color. Specular light more closely follows the classical rule of reflection wherein the angle of reflection equals the angle of incidence, as in Figure 5-5.
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Figure 5-5. Specular Reflection Angles.
As you might expect, the result of reflection of specular light depends greatly on the material properties of the surface. You may have noticed that in the real world surfaces that are smooth and "shiny" often show a small bright spot in bright, direct light. The bright spot is known as the specular highlight. With OpenGL you can give a surface the appearance of being smooth and shiny by producing such a bright spot. While the color of the surface with respect to ambient and diffuse light may vary, the color of the specular highlight tends toward white.
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