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.cursor/rules/roblox/physics/adaptive-timestepping.md
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---
title: Adaptive timestepping
description: Adaptive timestepping automatically assigns physical parts to varying simulation timesteps.
---
The Roblox physics engine simulates all parts inside the 3D workspace through Newton's second law of motion. This law of motion is solved over time via **timesteps** and a single timestep is done within a **worldstep** in Roblox.
By default, Roblox simulates physics at 240 Hz. Given cycles of approximately 60 frames per second, around 4 worldsteps are advanced per frame. With **adaptive timestepping**, the physics engine automatically assigns parts to three "solver islands" by varying their simulation timestep, with an emphasis on 60 Hz for best performance. However, parts that are "harder" to solve will use a faster timestep like 240 Hz to ensure physical stability.
<img src="../assets/physics/adaptive-timestepping/Diagram-Labels.png" alt="" width="100%" />
Assignment criterions are subject to change, but parts assigned to the 240&nbsp;Hz island include [assemblies](../physics/assemblies.md) with high velocity values, high acceleration values, and complex mechanisms that are hard to solve.
## Enable adaptive mode
To enable adaptive timestepping in Studio:
1. In the **Explorer** window, select the **Workspace** object.
<img src="../assets/studio/explorer/Workspace.png" alt="" width="320" />
2. In the **Properties** window, locate **PhysicsSteppingMethod** and select **Adaptive**.
<img src="../assets/physics/adaptive-timestepping/PhysicsSteppingMethod-Adaptive.png" alt="" width="320" />
To observe the timestepping process in action, you can open the Studio **Microprofiler** (<kbd>Ctrl</kbd><kbd>F6</kbd>; <kbd>⌘</kbd><kbd>F6</kbd>). Once the experience is running, press <kbd>Ctrl</kbd><kbd>P</kbd> (<kbd>⌘</kbd><kbd>P</kbd>) to pause at the current frame.
Under the scope named **physicsStepped**, observe that the scope name of **worldStep** now reads **worldStep&nbsp;-&nbsp;Adaptive**.
<img src="../assets/physics/adaptive-timestepping/Adaptive-Timestepping-Microprofiler-A.png" alt="" width="80%" />
Hovering your cursor above **LDLPGSSolver::solve** will reveal the status of how many islands belong in each frequency bucket; **1dt&nbsp;Islands**&nbsp;(240&nbsp;Hz), **2dt&nbsp;Islands**&nbsp;(120&nbsp;Hz) and **4dt&nbsp;Islands**&nbsp;(60&nbsp;Hz).
<img src="../assets/physics/adaptive-timestepping/Adaptive-Timestepping-Microprofiler-B.png" alt="" width="80%" />
## Debug visualization
During testing, it may be useful to visualize frequencies for simulated parts. To enable this option:
1. Open [Studio Settings](../studio/setup.md#customization).
2. From the **Physics** tab, enable **Are Timesteps Shown**.
Once enabled, simulated parts will be outlined by their current simulation rate. If a part stops being simulated, either via the [sleep system](../physics/sleep-system.md) or a network ownership change, the part will no longer be outlined.
<img src="../assets/physics/adaptive-timestepping/Diagram-Labels.png" alt="" width="100%" />
<figure>
<video src="../assets/physics/adaptive-timestepping/Adaptive-Timestepping.mp4" controls width="100%"></video>
<figcaption>Simulated parts outlined by the color representing their current simulation rate</figcaption>
</figure>
## Fixed-rate scenarios
Adaptive timestepping can improve physics performance by up to 2.5 times and it is recommended in most cases. However, some experiences should use **Fixed** mode (240&nbsp;Hz), including:
Experiences that require highly accurate simulations and stability, such as racing games, "destruction" simulations, or experiences featuring complex mechanisms like tanks.
Simulations where most parts default to the 240&nbsp;Hz solver island (red outlines during [debugging](#debug-visualization)). When 240&nbsp;Hz islands interact with islands of different frequencies (60&ndash;120&nbsp;Hz), those islands are converted to 240&nbsp;Hz with an overhead that may negate any performance gains resulting from adaptive timestepping.