Inverse-Square Falloff
How light fades with distance
Also known as: Light falloff · Inverse square law light · Attenuation radius · Light attenuation · Light distance falloff
Definition
Inverse-square falloff is the rule that the brightness of a light falls with the square of the distance from it: twice as far means a quarter of the light. It is how real lights behave and what physically based engines use. Because the light never reaches exactly zero, engines add an attenuation radius, a distance after which the light is cut off, so that distant lights are skipped and performance is saved.
In production
Choose the light's intensity and its radius together: a radius that is too small clips the light and shows a visible edge on surfaces, and a very large one costs performance. In Unreal Engine, inverse-squared falloff is the default and the attenuation radius limits the light, and in Unity the range sets the limit. Older, non-physical engines and stylized projects often use a linear falloff, which is easier to control by eye.
