How can i properly make projectile hitboxes?

[Cozmicweb (Cozmic)]

@Dynamite2479

Can you show me some code of how it would look like?

This is a proof of concept and should ideally be implemented on the client rather than the server. I’ve written it on the server for now as I currently do not have enough time to write the full thing.

Script Inside ServerScriptService

local RunService = game:GetService("RunService")

-- Testing projectile part
local Projectile = Instance.new("Part")
Projectile.Size = Vector3.new(1, 1, 3)
Projectile.Position = Vector3.new(0, 20, 0)
Projectile:SetAttribute("CreationTime", tick()) -- Track the creation time for the interpolation function
Projectile.Anchored = true
Projectile.Parent = workspace

local Force = 2 -- Horizontal movement speed of the projectile
local Gravity = 2 -- Fall speed of the projectile

--- Quadratic interpolation function to calculate the projectile's position
-- @param startPos The starting position of the projectile
-- @param force The force applied to the projectile (used for air resistance)
-- @param currentTime The current time
-- @return The new position of the projectile
local function interpolate(startPos, force, currentTime)
	-- Calculate the vertical drop this frame, clamped to a maximum of 5 (terminal velocity)
	local drop = math.clamp(currentTime^2 / Gravity / force, 0, 5)

	-- Calculate the new position by subtracting the drop from the starting position
	local newPos = startPos - Vector3.new(0, drop, 0)

	return newPos
end

--- Function called every frame to update the projectile's position
local function heartbeat()
	-- Get the creation time of the projectile
	local creationTime = Projectile:GetAttribute("CreationTime")

	-- Calculate how long the projectile has existed
	local timeDifference = tick() - creationTime

	-- Set the new position for the projectile
	-- interpolate(Projectile.Position, Force, timeDifference) to get the new height
	-- Projectile.CFrame.LookVector to get the horizontal movement
	-- Projectile.Size.Z to avoid overlapping and skipping positions
	-- Increase the part's Z size to make it move faster
	Projectile.Position = interpolate(Projectile.Position, Force, timeDifference) + Projectile.CFrame.LookVector * Projectile.Size.Z
end

-- Connect the heartbeat function to the RunService.Heartbeat event
RunService.Heartbeat:Connect(heartbeat)

ProjectileExample.rbxl (52.8 KB)

@Dynamite2479

I thought you said it was bad for performance?

Unanchored parts would be bad for performance and have unreliable physics when used on the client. I used anchored parts and moved them with a RunService.Heartbeat connection.

@Dynamite2479

--Code for the hitbox here, what im trying to figure out

Create a Region3 to represent the projectile on the server, then use the interpolation function I provided to move that region forwards. Use Workspace:GetPartBoundsInBox to check for collisions.

@Dynamite2479

LinearVelocity.VectorVelocity = Direction.Unit * Force

You could use the interpolation function to visualize the movement of the part by updating its position, or have the server send the Region3 location to the client, and use that to visualize the part.

Additionally, optimize the collision detection logic and part movement using something like batch processing before using it in production.

[Dynamite2479 (Ascension)]

I went into the project and it works but I have some questions.

@Cozmicweb

or have the server send the Region3 location to the client, and use that to visualize the part

Im guessing by remote events?

@Cozmicweb

batch processing

Also what is this?

[Cozmicweb (Cozmic)]

@Dynamite2479

Im guessing by remote events?

Yes

@Dynamite2479

Also what is this?

Instead of creating separate RunService.Heartbeat connections for each part’s collision detection, create a single connection that loops through a table of all the projectiles and processes them simultaneously. However, consider using BasePart.Touched first, as it may be more performant if it works correctly.

[Dynamite2479 (Ascension)]

Yeah it would be my last resort using touched events for heavy physics based projectiles

[Dynamite2479 (Ascension)]

I didnt really find a answer to this question but i found some helpful topics like:

Network Efficient and Safe Practices with Projectiles

After a lot of research and practice done on my part after asking this question myself several months ago, I’ve decided to shed some light for everyone on some more efficient network practices when it comes to projectiles and their hitboxes. Games with lots of stuff going on shouldn’t have to have 150+ kb/s of network traffic all the time. A few key things to note before diving deeper into this: There are lots of ways to go about doing these depending on your use-case, and 95% of the time, i…

This works for linear projectiles with a predictable path but not really what im looking for

[dthecoolest]

@Dynamite2479

This works for linear projectiles with a predictable path but not really what im looking for

If you do not want it to be linear you can modify the equation.

Currently the equation is this on the Z axis

local projectileTime =  (respondedTick - startTickVal)
local positionCFrame = spawnPoint * CFrame.new(0, 0, -45 * projectileTime )

If you want it to randomly start moving diagonally at 5 seconds in linearly you can use an if statement.

local projectileTime =  (respondedTick - startTickVal)

if projectileTime > 10 then
--Start moving in X axis instead
local positionCFrame = spawnPoint * CFrame.new( -45 * (projectileTime-10), 0, -45 * projectileTime )

else
local positionCFrame = spawnPoint * CFrame.new(0, 0, -45 * projectileTime )
end

You can even instead of just making it swerve 10 seconds in you can use math.random instead to make it even more unpredictable yet predictable.

You can also even add a quadratic equation instead to make a curved behavior.

local positionCFrame = spawnPoint * CFrame.new(0, 0, -45 * projectileTime^2 -5*projectileTime )

The concept I did above was actually similar but not the same as fastcast using piecewise functions to seperate the projectile motions into sections.

@Xan_TheDragon

• There is a list of each individual section of the cast’s motion! To get the dynamic stuff to work, casts had to be turned into piecewise functions. The table storing the data for each piece is exposed (check out the API) so you can do whatever you might want with the information.

[Dynamite2479 (Ascension)]

I know how do to everything you said except the equation.

@dthecoolest

You can also even add a quadratic equation instead to make a curved behavior

This was what i was looking for but i dont know how to implement it i know the rest of what you said but i usually use roblox physics to move my projectile.