Lerping Roblox

Understanding Lerping in Roblox Development

Lerping in Roblox is just linear interpolation — moving a value from point A to point B smoothly over time. That is the entire concept distilled down. Most people learn it because they want their camera to track smoothly, their GUIs to fade in without snapping, or their characters to animate without looking stiff. But there is a lot more nuance here than the standard tutorial will tell you. You call something every frame, pass it a t value between 0 and 1, and it returns the interpolated result. The simplest version looks like this: local start = workspace.Part.CFrame
local goal = workspace.Part2.CFrame

game:GetService("RunService").RenderStepped:Connect(function(dt)
  currentT = math.clamp(currentT + dt / duration, 0, 1)
  local newCFrame = start:Lerp(goal, currentT)
  workspace.Part.CFrame = newCFrame
end)

That works fine in isolation. It works fine when you are testing in Studio with one object moving. It breaks down when you are running twenty-five simultaneous lerps across a crowded server and wondering why your frame rate drops to single digits on weaker machines. I learned that the hard way during a project where I had a dynamic terrain transition system that used per-tile CFrame lerps driven by RenderStepped. The lerp math itself was not the bottleneck — the problem was creating twenty-five separate CFrame assignments per frame on the client while also replicating state over the network. I ended up batching everything into a single updated property per frame and moving the interpolation to a local coroutine rather than directly wiring it to RenderStepped. That cut my frame time roughly in half without changing the visual result at all.

Lerping Roblox objects effectively requires understanding replication costs

Here is a detail that nobody bothers to mention in the basic guides: lerp values should almost never be replicated over the network. You replicate the start position, the goal position, and maybe a flag telling the client to begin interpolating. The actual t value and intermediate results stay entirely local. I used to see developers send the interpolated position back to the server every frame thinking it was required for sync. It is not. The server only needs to know where the object started and where it is supposed to end. Everything in between is client-side calculation. Sending that data back and forth is what causes stutter and bandwidth issues in multiplayer lerp systems. Another common mistake is using RunService.Heartbeat instead of RenderStepped or vice versa without realizing the timing implications. Heartbeat runs after physics simulation, which means if you are lerping a part position and then reading it for collision or pathfinding, you are working with stale data from the previous frame. RenderStepped aligns better with the rendering pipeline for visual lerps. Physics-based lerps belong on Stepped if you need them to interact correctly with the physics engine. Getting this wrong does not crash your game, but it produces jerky movement that players will notice even if they cannot articulate why. The t value progression is also usually handled wrong. Most tutorials show a linear t increase, which produces movement that starts and stops abruptly. That is technically correct interpolation, but it feels terrible in practice. You typically want to apply an easing function. Something as simple as easing the t value through a quadratic or cubic curve before passing it to the lerp makes the difference between robotic and polished. The math is straightforward and the performance cost is negligible.

There is also the question of whether to use CFrame:Lerp, Vector3:Lerp, or manual interpolation. CFrame:Lerp uses spherical linear interpolation for rotation, which means it will take the shortest rotational path. That is usually what you want, but not always. If you are lerping a door that needs to swing open one full rotation, CFrame:Lerp will snap it the other direction. In that case you handle the rotation component manually and only lerp the position. I spent an afternoon debugging a gate animation that kept closing the wrong way before I realized CFrame:Lerp was optimizing the rotation path against my intent. If you are building something more complex like a camera system or a boss ability that requires interpolation across multiple axes simultaneously, you might want to look at existing community modules rather than writing from scratch. Libraries like ProfileService or custom coroutine-based lerp managers handle edge cases like partial completion on reconnect and delta time compensation across frame rate variance. These are the problems that turn a simple lerp system into a maintenance burden if you do not account for them early. The core takeaway is that lerping itself is trivial to implement. What makes it work well in Roblox is understanding where the interpolation lives — client or server — how it interacts with the frame loop, whether replication is actually needed, and what easing or rotation behavior you require. Miss any of those and the lerp will function but feel wrong or perform poorly under load.