attenuate

general purpose attenuation functions (linear, quadratic, etc.)

api

These functions are generic, but described in terms of representing a light source. They take the form of

result = attenuationType(distance, maxDistance)

maxDistance specifies the maximum distance attenuation can occur over. For example if you are simulating a light source, and don't want the light to have any contribution beyond a distance of 500, set maxDistance to 500.

result is a value from 0.0 -> 1.0 with 0.0 being complete attenuation, and 1.0 being no attenuation.

linear

The decline of this type of falloff is linear, inversely proportial to the distance from the source:

I = 1/d

where I is intensity and d is distance). This means that the intensity (set by its magnitude/brightness) will diminish (at a fixed rate) as it travels from its source.

In the real world a 100% linear lightsource would be practically impossible, as it would represent a real world soft light of infinite size, but in the virtual world, a 0:1:0 lightsource is believable for most entity based lightsources.

result = linear(distance, maxDistance)

quadratic

The attenuation of a 100% quadratic light is exponential (quadratic), expressed as:

I = 1/d^2

meaning that the further the light travels from its source, the more it will be diminished. This creates a very sharp drop in light.

A quadratic lightsource represents a pure "point light source" in the real world. In the virtual world, this effect looks like a lightsource shining through murky water, looking far from typical real world lightsource behavior.

When used in moderation, quadratic attenuation can be used not only for small lightsources, but also to reflect light travelling through something more dispersing than air, like air humidity (like fog) or water.

result = quadratic(distance, maxDistance)

example

import { linear } from 'attenuate'


const maxDistance = 1000
console.log(linear(0, maxDistance))     // 1.0
console.log(linear(100, maxDistance))   // 0.9
console.log(linear(500, maxDistance))   // 0.5
console.log(linear(1000, maxDistance))  // 0.0
console.log(linear(1001, maxDistance))  // 0.0