Denizen Herding Behavior

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This article is by Russell Ackerman. I thought I would share my success at getting my deer to herd in my roguelike, I did it by doing this: This article relates to the LUA programming language Sound propogates out from a square, dropping informatino about itself. The function is as follows:

function funcs.makesound(intensity,activator,x,y,z)

-- print("Making a sound .."..intensity.." from "..activator["name"].." X "..x.." Y "..y.." Z "..z)

local objectloc = data.objectloc --contains [x][y][z][object with internal data]

local working, future = {}, { {x,y,z} }

local soundscape = data.soundscape --where your sound data is stored, per tile [x][y][z][thesound][various keys like strength]

local finished = {}

local insert = table.insert

local tiles = data.tiles

local checkforedgeofmap = funcs.checkforedgeofmap --so sound doesnt go off the edge of your limited world.

finished[x] = {}

finished[x][y] = {}

finished[x][y][z] = 1

soundscape[x][y][z][activator] = soundscape[x][y][z][activator] or {} --for moveenemytowards

insert(soundscape[x][y][z][activator],{["strength"] = intensity})

local counter = intensity

while(counter <= intensity and counter >= 1) do

counter = counter - 1 --this keeps track of how strong the sound is when it gets to the square.

working,future = future, {}

local x,y,z

for k,v in pairs(working) do

for x = v[1]- 1,v[1] + 1 do

finished[x] = finished[x] or {}

for y = v[2] -1,v[2] + 1 do

finished[x][y] = finished[x][y] or {}

for z = v[3] - 1,v[3] + 1 do --now we're iterating over the nine squares around the center square, on the first iteration.

if z < data.amountofzlevels and z >= 1 and (not checkforedgeofmap(x,y)) and (not finished[x][y][z]) and (not tiles[x][y][z]["filled"]) and (not tiles[x][y][z]["open"]) the

finished[x][y][z] = 1


soundscape[x][y][z][activator] = soundscape[x][y][z][activator] or {} --for moveenemytowards

insert(soundscape[x][y][z][activator],{["strength"] = counter})

--the following visualizes the sound data.

-- slang.gotorc(y+data.mapoffsety,x+data.mapoffsetx)

-- slang.setcolor(counter)

-- slang.writechar("*")

-- slang.refresh()








Data about the "soundscape" is stored, for now, just with the data of who made the sound and how intensly it was heard at the square. soundscape[x][y][z][the object that activated it][irreleveant key][strengthofsound] and any other pertinent variables about the noise would also be stored there.

To use this data in pathfinding to get your denizens to herd, simply do the following:

1/x times that the creature activates pathfinding to choose a square with the shortest path, simply weight the RELATIVE VALUE of those squares. Squares with more noise generated by creatures who are the same species as me should be weighted with an amount relative to the total noise on that square from those animals except myself, weighted to be MORE valuable, but only one out of x times - this fractional usage allows the creature to break from the herd and stop herding behavior once it cant hear any sound at all from those of its own species. Its a simple matter of using a function like "total_sound_at_square_except_me(me,x,y,z).

My code for moving the denizens is at follows. the table "Distances" is a table of data in the form distances[x][y][z] = amount, where distances[x][y][z] is the distance of a particular square to the destination square. It's a little hokey but it's pretty simple too:

All I do is subtract sound from distance, and select the square with the "lowest" relative value to move the denizen to.

function funcs.totalsoundfromob(ob,x,y,z)

--print("Totaling sound")

local soundscape = data.soundscape

local totalstr = 0

for k2,v2 in pairs(soundscape[x][y][z][ob]) do

totalstr = totalstr + v2["strength"]


return totalstr


function funcs.totalsoundatspot(ob,x,y,z) --totals sounds at spot from "my species"

local soundscape = data.soundscape

local sound

local totalstrength = 0

local numfriends = 0

for k,v in pairs(soundscape[x][y][z]) do

if ob["species"] == k["species"] and k ~= ob and (not k["isplayer"]) then --not k isplayer for sanity purposes.

sound = funcs.totalsoundfromob(k,x,y,z)

totalstrength = totalstrength + sound

numfriends = numfriends + 1



-- print("total strength "..totalstrength)

return totalstrength, numfriends


--ob contains ob.x and ob.y and ob.z, targ contains targ.x,y,z etc. --if called without "targ" object, it moves to a random square.

function funcs.moveenemytowards(ob,targ)

-- print("Moving "

-- if targ then print("Towards"..targ.x.." "..targ.y.." "..targ.z.." from "..ob.x.." "..ob.y.." "..ob.z) end

local numfriends

local soundonhomesquare, numfriends = funcs.totalsoundatspot(ob,ob.x,ob.y,ob.z)

local distances

-- if not targ and ob.activateherding and soundonhomesquare < 0 then --if i dont hear anything and im supposed to be moving randomly

if targ and then print("Targ name " end

-- print("Starting pathfinding")

if targ then funcs.pathfindfromto(ob,targ) distances = ob.distances end --gets a path... checks for a new path every so often.

-- if not targ then distances = nil end

-- print("Finished pathfinding")

local soundscape = data.soundscape

local totalsound

local oldx,oldy,oldz = ob.x,ob.y,ob.z

--print("MOVING A MONSTER!!")

local x local y

local z

local lowestdistance = {distance = 1000000 ,x=oldx,y=oldy,z=oldz} --HARDCODED LIMIT

local iterations = 0

local movementintelligence

if ob.movementintelligence then movementintelligence = ob.movementintelligence

else movementintelligence = 20 end

while(iterations < movementintelligence) do

iterations = iterations + 1

x = math.random(ob["x"]-1,ob["x"]+1)

y = math.random(ob["y"]-1,ob["y"]+1)

z = math.random(ob["z"]-1,ob["z"]+1)

-- for x = ob["x"] -1,ob["x"] + 1 do iterating in this pattern makes us select the upper left corner...

-- for y = ob["y"] -1,ob["y"] + 1 do

-- for z = ob["z"] -1,ob["z"] + 1 do

if ((not targ) and (not funcs.checkforblockpassageofpath(x,y,z))) or (targ) then

local relativevalue = 0

if ob.activateherding then totalsound = funcs.totalsoundatspot(ob,x,y,z) end

if targ and not distances then return end --at destination already

if ((not targ) or (distances and distances[x] and distances[x][y] and distances[x][y][z])) and not funcs.checkforedgeofmap(x,y) then --was and distances[x][y][z]

if targ then relativevalue = distances[x][y][z] + relativevalue end

--print("SOUND "..soundonhomesquare)

local soundvariable

local usesoundvariable = true

if ob.tightgroups then soundvariable = ob.prefersoundlevel * numfriends end

if ob.loosegroups then soundvariable = ob.prefersoundlevel end

if ob.prefersoundlevel == 0 then usesoundvariable = false end

if (not targ) and ob.activateherding and soundonhomesquare == 0 then --if i dont hear anything and have no target, choose a random square.

relativevalue = relativevalue - (math.random(1,1000) * 10)

elseif ob.activateherding and (usesoundvariable and (soundonhomesquare < (soundvariable)) or not usesoundvariable) and soundonhomesquare > 0 then --if sound is lower than threshhold, herd a FRACTION of the time..

if math.random(1,ob.herdingtendency) == 1 then relativevalue = relativevalue - (totalsound * 10) end --herd according to a fraction of times ob.herdingtendency should be 10 or 20 or 5 or whatever. If im beyond the sound range by not herding, i wont herd from that point until i hear more sound..

elseif (not targ) then --if i dont care about sound, move randomly.

relativevalue = relativevalue - (math.random(1,1000) * 10) --was +


if relativevalue < lowestdistance["distance"] then --go towards high strength sound

lowestdistance = {["distance"] = relativevalue,["x"]=x,["y"]=y,["z"]=z}



end --ends if not targ...

-- end

-- end

-- end

end --ends iterations over intelligence...


-- funcs.drawspotsimple(oldx,oldy,oldz,nil,ob)


--so as you can see the "relative value" of the square gets changed depending on how much sound is detected nearby.

Hope this helps someone! Check out my game Ascii Wilderness, which is open source LUA.

In this game, the deer properly herd together based on their internal variables. This code also depends on some internal herding variables from the participants such as "activateherding = 1" and "tightgroups" or "loosegroups" = 1 and "prefersoundlevel" = amount and also "herdingtendency" = 3- 10

Using this code, my ghouls will wait up for other nearby ghouls before closing in for the attack. Sweet!

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