nerv.lua

nerv.lua is inspired by nerve impulses for controlled randomness

You need to supply your own noise function if you are using this library on a platform other than love2d

View the topic regarding this library on love2d

Situations where nerv might be useful:

• make birds fly/frogs jump/fog lift randomly when player approaches
• make enemies attack player randomly when player approaches and drastically reduce the chance of enemies attempting to attack when obstructed by obstacle
• make customers leave the store with increasing chances as the waiting time increases
• make interesting interactive patterns

Installation

local nerv = require 'nerv'

--initiation
local new_nerv = nerv()

--update each instance
function love.update(dt)
  ...
  new_nerv:update(dt)
  ...
end

Basic Idea

nerv.lua mimics the behaviour of membrane potential of actual nerve cells. In each frame, stimuli sent to an instane of nerv will triger a change in its potential. If this value increases above the value of threshold potential, it will change drastically for the refractory period. During this period, the potential of that nerv instance will not be affected by any stimulus.

(If you are keen to understand the biological basis of nerv.lua, this, this, this and this may help.)

Documentation

Initiation of a new nerv instance

Synopsis

new_nerv = nerv(fn_onStart, fn_onFinished, maxPotential, refractoryPeriod, noiseFn)

Examples

new_nerv = nerv(  _add_bird, _, 3, .6)

--initiate and change its properties later
new_nerv = nerv()
new_nerv:setFunctions(function() truck:move() end, function() truck:stop() end)

--initiate with chained functions
new_nerv = nerv():setFunctions(function() truck:move() end, function() truck:stop() end)

Arguments

fn_onStart (null function) function that is called when potential reaches threshold potential

fn_onFinished (null function) function that is called at the end of refractory period

maxPotential (8) maximum potential that potential will reach after exceeding threshold potential

refractoryPeriod (1) period of time when stimuli have no effect on potential when potential is undergoing massive change (if refractory period is 0, then the potential value of the nerv instance will not undergo a massive change when it exceeds threshold potential)

noiseFn Supply your own noise function if you are not using love2d

Sending stimulus

Synopsis

function love.update(dt)
  ...
  new_nerv:send(strength)
  ...
  new_nerv:update(dt)
end

Example

local _distance = math.sqrt( (player.x-mx)^2 + (player.y-my)^2 )
local _inv = 1/distance
local strength = _inv * 100
new_nerv:send(strength)

Argument

strength (0) is the strength of the stimulus that is sent to that nerv instance. (the larger the strength, the more likely threshold potential will be reached)

Applying inhibition

Synopsis

new_nerv:inhibit(strength)

Example

if Obstacle.isInPath() then
  new_nerv:inhibit(10000)
end

Argument

strength (0) is the strength of inhibition applied to that nerv instance. Basically it is the negative of stimulus.

Get potential

Synopsis

new_nerv:getPotential()

Example

--love.update
local p = new_nerv:getPotential()
particle.actual_y = particle.y + p
...
--love.draw
love.graphics.circle('fill',particle.x,particle.actual_y)

Connect nerv instances together

Synopsis

new_nerv:connect(n,lagTime)

Example

local nerv = require 'nerv'
...
local nervs = {}
for n = 1,10 do
  table.insert( nervs, nerv() )
end
for n = 2,9 do
  nervs[n]:connect( nervs[n+1], .2 )
  nervs[n]:connect( nervs[n-1], .2 )
end

Arguments

n is the nerv instance to be connected downstream, meaning that if this nerv instance reaches threshold potential and fire off, then the nerv(s) connected to it will directly fire off after lagTime. lagTime (.1) delay before nerve impulse is fired to the connected nerv instance

Set various properties

:sync()

• Used when creating many nerv instances together. These nerv instances will have similar potential variations.

:setSkipped()

• Skip tweening. It is advised to skip tweening when you do not need to use the value of potential (faster by about 1/3 of the time).

:setPotentials( maxPotential, restingPotential, thresholdPotential, isReverseMP )

restingPotential is the value of the potential when no stimulus is applied thresholdPotential is the value above which a massive change in potential will be triggered( to reach maxPotential ) isReverseMP indicates whether the value of potential should drop to the negative of maxPotential after maxPotential has been reached( all during the refractory period )

:setFunctions(fn_onStart, fn_onFinished)

:setPeriod(refractoryPeriod)

:setNoiseFn(noiseFn)

Examples

local new_nerv = nerv():setFunctions( function() Sounds.bird:play() end, _ ):setPeriod(.6):setSkipped():setPotentials(3)

local nervs = {}
for n = 1,10 do
  table.insert( nervs, nerv():sync():setSkipped() )
end