Optimize Rigidbody component collision detection modes

Set the CollisionA collision occurs when the physics engine detects that the colliders of two GameObjects make contact or overlap, when at least one has a Rigidbody component and is in motion. More info
See in Glossary Detection mode on a Rigidbody component in the InspectorA Unity window that displays information about the currently selected GameObject, asset or project settings, allowing you to inspect and edit the values. More info
See in Glossary 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 RigidbodyA component that allows a GameObject to be affected by simulated gravity and other forces. More info
See in Glossary component collision detection modes, refer to Rigidbody component reference.

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 colliderAn invisible shape that is used to handle physical collisions for an object. A collider doesn’t need to be exactly the same shape as the object’s mesh - a rough approximation is often more efficient and indistinguishable in gameplay. More info
  See in Glossary 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) to ensure the GameObjectThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
  See in Glossary 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 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 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
• Managing time and frame rate
• Memory Profiler
• Physics Project Settings
• Rigidbody component reference
• Collision detectionAn automatic process performed by Unity which determines whether a moving GameObject with a Rigidbody and collider component has come into contact with any other colliders. More info
  See in Glossary
• Sweep-based CCD
• Speculative CCD