Introduction
Hello everyone! In this tutorial, I’m going to teach you how to create a realistic NPC eyesight system so NPCs can see and detect players and other objects. For example, you could use this to make a guard detect a player.
Steps
-
Create a script in
ServerScriptServiceand name it whatever you’d like. This script will control every NPC with eyesight. -
Give the NPCs you want to have eyesight a tag named “NPC” and the objects you want to NPC to detect a tag named “Detectable.” Players will be automatically detected. The “Detectable” tag may only be added to models.
-
Start defining the variables in your script.
local PlayerService = game:GetService("Players")
local CollectionService = game:GetService("CollectionService")
local npcModels = CollectionService:GetTagged("NPC")
local viewRange = 30 -- How far the NPC can see in studs
local fieldOfView = 70 -- The NPC's field of view in degrees
local objectLastDetected = nil -- The object the NPC last saw
- Create a
getCharactersfunction. This function will return atableof every player’s character in the game.
local function getCharacters()
local characters = {}
local players = PlayerService:GetPlayers()
for index, player in players do
table.insert(characters, player.Character)
end
return characters
end
- Next, create a
raycastfunction. This function will be used to check if anything is blocking the NPC’s line of sight, as it cannot see through walls.
local function raycast(npc, start, finish)
local parameters = RaycastParams.new()
parameters.FilterDescendantsInstances = {npc, getCharacters()}
parameters.FilterType = Enum.RaycastFilterType.Exclude
local raycast = workspace:Raycast(start, (finish - start), parameters)
if raycast then
return true
else
return false
end
end
- Now, create a
checkSightfunction. We will use this to determine whether/not an object is being seen by the NPC.
local function checkSight(npc)
local detectable = {}
local characters = getCharacters()
local taggedObjects = CollectionService:GetTagged("Detectable")
for index, character in characters do
table.insert(detectable, character)
end
for index, object in taggedObjects do
table.insert(detectable, object)
end
for index, object in detectable do
if object:IsA("Model") then
object = object.PrimaryPart
end
local headPosition = npc.Head.Position
local objectPosition = object.Position
local headCFrame = npc.Head.CFrame
local direction = (objectPosition - headPosition).Unit
local lookVector = headCFrame.LookVector
local dotProduct = direction:Dot(lookVector)
local angle = math.deg(math.acos(dotProduct))
local distance = (headPosition - objectPosition).Magnitude
if angle > fieldOfView then
continue
end
if distance > viewRange then
continue
end
if raycast(npc, headPosition, objectPosition) then
return
end
if object:IsA("Model") then
objectLastDetected = object.Parent
else
objectLastDetected = object
end
return true
end
end
- Lastly, create a
forloop that goes through every NPC and sets up detection every second with error prevention.
for index, npc in npcModels do
local humanoid = npc:FindFirstChildOfClass("Humanoid")
if not npc:IsA("Model") then
continue
end
if not humanoid then
continue
end
local function checking()
while task.wait(1) do
if checkSight(npc) then
-- Code for when an NPC sees a detectable object
else
-- Code for when an NPC does not see a detectable object
end
end
end
coroutine.wrap(checking)()
end
Resources
Dot Product - Wikipedia
Coroutine - Roblox Documentation
-- Formula for distance (in studs)
local distance = (pointA.Position - pointB.Position).Magnitude
Conclusion
Thank you for checking out my tutorial! If you have any questions, let me know in the comments down below.
If this tutorial helped you, please consider leaving a like! 
