Understanding light decay

When working with lights in a computer graphics application, typically speaking, there are two options available to help us control the distance that light is allowed to travel in a scene. One is attenuation, which is generally a forced cut off point beyond which light isn't allowed to travel. A typical set of controls for attenuation would involve values that can be set for both near and far cut off points or distances in the scene.

One important thing we need to keep in mind regarding attenuation, however, is that it is not a naturally occurring phenomenon. In the real world, light has no built-in mechanism whereby we can just tell it to stop travelling beyond a fixed point in space. If you have ever tried to create a completely blacked out environment, you will no doubt have wished that such a control was available, as light seems to find a way to travel in an environment no matter how hard you work to block it.

Decay or falloff, in contrast to attenuation, is...