# Optimize Rigidbody component collision detection modes

> Balance collision accuracy and CPU performance by choosing appropriate detection modes for Rigidbody components.

Set the Collision Detection mode on a [**Rigidbody**](/engine/6000.3/manual/physics-section/physics-overview/rigidbody/class-rigidbody.md) component in the Inspector window to balance simulation accuracy, and prevent phenomena such as fast-moving objects from passing through other objects, against CPU performance.

When you enable **Collision Detection** modes, always profile and monitor performance. Some **Collision Detection** modes, especially **Continuous** and **Continuous Dynamic**, can significantly impact CPU usage. Apply them selectively and only where needed.

To learn more about Editor component collision detection modes, refer to [Rigidbody component reference](/engine/6000.3/manual/physics-section/physics-overview/rigidbody/class-rigidbody.md).

The available collision detection modes include:

* **Discrete**: Checks for collisions only at the discrete time points of each physics simulation step. This is the default collision detection mode and the most performant. The risk when using **Discrete** is that fast objects can tunnel if they pass entirely through another collider between physics steps. Use **Discrete** for most objects, especially when they aren't exceptionally fast or where occasional tunneling is acceptable.
* **Continuous**: Prevents tunneling through static geometry. Uses [sweep-based continuous collision detection (CCD)](/engine/6000.3/manual/physics-section/physics-overview/collision-section/collision-detection/continuous/sweep-based-ccd.md) to ensure the GameObject does not pass through static (GameObjects without a **Rigidbody** component or Kinematic **Rigidbody** component) colliders. **Continuous** is more resource-intensive than **Discrete**. **Continuous** does not guarantee tunneling prevention against other dynamic **Rigidbody** components unless they are set to **Continuous Dynamic**. Use **Continuous** for fast objects where preventing tunneling through static level geometry is important and **Continuous Speculative** isn't sufficient.
* **Continuous Dynamic**: Uses [sweep-based CCD](/engine/6000.3/manual/physics-section/physics-overview/collision-section/collision-detection/continuous/sweep-based-ccd.md) against both static colliders and other **Rigidbody** components that are also set to **Continuous Dynamic** or **Continuous**. **Continuous Dynamic** has the highest CPU usage and that usage increases with the number of potential interactions. Use sparingly and only for critical, very fast-moving objects that absolutely must not tunnel through other specifically-marked fast-moving dynamic objects.
* **Continuous Speculative**: Uses a [Speculative CCD](/engine/6000.3/manual/physics-section/physics-overview/collision-section/collision-detection/continuous/speculative-ccd.md) approach to prevent tunneling against both static and dynamic colliders. Often the best choice for CCD. **Continuous Speculative** is generally balanced performance and simulation quality. It is often more performant than **Continuous** modes for similar or better tunneling prevention. Use **Continuous Speculative** when **Discrete** mode results in tunneling for fast-moving objects.

To determine the ideal **Collision Detection** mode for a **Rigidbody** component, the recommended best practice is to:

* Start with the **Discrete** mode for most **Rigidbody** components. **Discrete** is the most performant and sufficient for most objects that don't move exceptionally fast or where occasional tunneling is acceptable.
* If tunneling occurs with fast objects, switch to **Continuous Speculative**.
* If tunneling still occurs with **Continuous Speculative** or you want to have specific interactions with static geometry, switch to **Continuous**.
* Set to **Continuous Dynamic** only as a last resort for critical object-on-object tunneling.

## Additional resources

* [Unity Profiler](/engine/6000.3/manual/analysis/profiler.md)
* [Managing time and frame rate](/engine/6000.3/manual/scripting/managing-time-and-frame-rate.md)
* [Memory Profiler](https://docs.unity3d.com/Packages/com.unity.memoryprofiler@latest)
* [Physics Project Settings](/engine/6000.3/manual/unity-editor/editor-settings-reference/comp-manager-group/class-physics-manager.md)
* [Rigidbody component reference](/engine/6000.3/manual/physics-section/physics-overview/rigidbody/class-rigidbody.md)
* [Collision detection](/engine/6000.3/manual/physics-section/physics-overview/collision-section/collision-detection.md)
* [Sweep-based CCD](/engine/6000.3/manual/physics-section/physics-overview/collision-section/collision-detection/continuous/sweep-based-ccd.md)
* [Speculative CCD](/engine/6000.3/manual/physics-section/physics-overview/collision-section/collision-detection/continuous/speculative-ccd.md)