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Physics

There are many different ways to do physics in multiplayer games. Netcode for GameObjects (Netcode) has a built in approach which allows for server authoritative physics where the physics simulation is only run on the server. To enable network physics add a NetworkRigidbody component to your object.

NetworkRigidbody#

NetworkRigidbody is a component which sets the Rigidbody of the GameObject into kinematic mode on every peer except the server. That way a realistic physics simulation can be run on the server and the resulting positions can be synchronized to the clients without any interference.

To use NetworkRigidbody add a Rigidbody, NetworkTransform and NetworkRigidbody component to your NetworkObject.

Some collision events are not fired when using NetworkRigidbody.

  • On the server all collision and trigger events (such as OnCollisionEnter) will fire as expected and you can access / modify values of the Rigidbody such as velocity.
  • On the clients the rigidbody will be kinematic. Trigger events will still be fired but collision events will not be fired when colliding with other networked rigidbodies.
tip

If there is a need for a gameplay event to happen on a collision you can listen to OnCollisionEnter function on the server and synchronize the event via ClientRpc to all clients.

NetworkRigidbody2D#

NetworkRigidbody2D works in the same way as NetworkRigidbody but for 2d physics (Rigidbody2D) instead.

NetworkRigidbody & ClientNetworkTransform#

NetworkRigidbody can be used in combination with the ClientNetworkTransform package sample to allow the owner client of a NetworkObject to move it authoritatively. In this mode collisions will only result in realistic dynamic collisions if the object is colliding with other NetworkObjects which are owned by the same client.

note

Add the ClientNetworkTransform component first to your GameObject else the NetworkRigidbody will automatically add a regular NetworkTransform.