How to make a Roblox pathfinding NPC (with AI)

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5 files · 170 lines · 42 seconds · 1 credit

Sample output: ServerScriptService/NPCBrain.lua

--!strict
-- ServerScriptService/NPCBrain.lua  (Forge AI · excerpt)
local PathfindingService = game:GetService("PathfindingService")
local Players = game:GetService("Players")
local ReplicatedStorage = game:GetService("ReplicatedStorage")
local NPCConfig = require(ReplicatedStorage.Modules.NPCConfig)

type State = "idle" | "chase" | "attack"

local function findTarget(npc: Model, sightRange: number): Player?
    local pos = npc.PrimaryPart.Position
    local closest, closestDist = nil, sightRange
    for _, player in ipairs(Players:GetPlayers()) do
        if not player.Character or not player.Character.PrimaryPart then continue end
        local d = (player.Character.PrimaryPart.Position - pos).Magnitude
        if d < closestDist then closest, closestDist = player, d end
    end
    return closest
end

local function moveToward(npc: Model, target: Vector3, config)
    local hum = npc:FindFirstChildOfClass("Humanoid") :: Humanoid
    local path = PathfindingService:CreatePath({
        AgentRadius = config.radius,
        AgentHeight = config.height,
        AgentCanJump = true,
        AgentJumpHeight = 7,
    })
    local ok = pcall(function() path:ComputeAsync(npc.PrimaryPart.Position, target) end)
    if not ok or path.Status ~= Enum.PathStatus.Success then return end
    for _, wp in ipairs(path:GetWaypoints()) do
        if wp.Action == Enum.PathWaypointAction.Jump then hum.Jump = true end
        hum:MoveTo(wp.Position)
        hum.MoveToFinished:Wait()
    end
end

local function brain(npc: Model)
    local config = NPCConfig[npc:GetAttribute("NPCType") or "default"]
    npc:SetAttribute("State", "idle" :: State)
    while npc.Parent do
        local state = npc:GetAttribute("State") :: State
        local target = findTarget(npc, config.sightRange)
        if state == "idle" and target then npc:SetAttribute("State", "chase") end
        if state == "chase" and target then
            moveToward(npc, target.Character.PrimaryPart.Position, config)
            local dist = (target.Character.PrimaryPart.Position - npc.PrimaryPart.Position).Magnitude
            if dist < config.attackRange then npc:SetAttribute("State", "attack") end
        end
        task.wait(0.5)
    end
end