Is it possible to start a tween at a specified timestamp?

Help and Feedback Scripting Support
#1

You can write your topic however you want, but you need to answer these questions:

  1. What do you want to achieve? Keep it simple and clear!
    I would like to start a tween at a specified timestamp

  2. What is the issue? Include screenshots / videos if possible!
    I’m tweening something on the client that I want to sync up to the server, this could sync up at any time, the easing style is not linear, so it’s not like I can just change the length of the tween to whatever’s left.

I’m not tweening on the server because that would cost a lot of performance having to replicate every update each frame, so using the clients to tween and the server sending the end goal would be a lot better.

  1. What solutions have you tried so far? Did you look for solutions on the Developer Hub?
    I’ve searched everywhere online, I can’t find a topic even discussing it, also tried custom tweening scripts, but they are a lot less performant than Roblox’s C# TweenService.
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#2

:Play() the tween whenever something is triggered.

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#3

:Play() will play the tween from the start, which is not what I’m looking for

#4
#5

I’m not always playing from 0.5, random values so this won’t work, I’m also using quad not sine

#6

You can use TweenService:GetValue to tween from a custom starting and ending point:

local TweenService = game:GetService("TweenService")

-- duration of the tween
local duration = 3

-- where you want the tween to start/stop
-- from 0 to 1 normally
local startTime = 0.3
local finishTime = 1

-- part to tween or whatever
local obj =

-- where you want the value to tween to/from
-- can be any data type
local startValue = Vector3.new(0, 0, 0)
local finishValue = Vector3.new(0, 0, 1)


local adjustedLength = finishTime - startTime
local i = 0
while i < 1 do
    local dt = task.wait()

    i = math.min(i + dt/duration, 1)

    -- transform from [0, 1] to [startTime, endTime]
    local preAlpha = i * adjustedLength + startTime

    local alpha = TweenService:GetValue(
        preAlpha,
        Enum.EasingStyle.Quad,
        Enum.EasingDirection.Out
    )

    -- transform from [startTime, endTime] to [0, 1]
    local postAlpha = (alpha - startTime) / adjustedLength

    -- apply `postAlpha` to a lerping function
    obj.Position = startValue:Lerp(finishValue, postAlpha)
end

Edit: This would actually lead to the value jumping up to wherever 0.3 is, oops
Edit 2: It should be fixed :+1:
Edit 3: should actually be fixed
Edit 4: should actually be fixed [2]

I would like to note that it would be difficult to make a tween-like interface for this, but it’s still possible anyway.

I suppose it can be made simpler with coroutines:

local function partialTween(...)
    -- code up there I guess
end

-- when you want the tween to start
local tweenThread = task.spawn(
    partialTween,
    -- cool arguments
)

-- when you want the tween to stop
task.cancel(tweenThread)
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