NetworPlayerState struct (Experimental)

[NiftyliuS]

Network Player State Struct

This struct is intended to transfer the most common states used for desync detection and reconciliation as efficiently as possible
( see diagram ) with addition of 3 functions that meant to simplify the process.

1. Ability to pass defaults in the constructor.

NetworkPlayerState updatedState = new NetworkPlayerState(NetworkPlayerState? defaults);

This is meant to allow easy cloning of the struct while retaining the ability to change any one of the memebers

var previousState = new NetworkPlayerState(){ .... }
var newState = new NetworkPlayerState(previousState ){ Position= new Vector3( x, y, z ) }

2. Ability to compare and extract changes.

NetworkPlayerState changes = new NetworkPlayerState().GetChangedStateComparedTo(NetworkPlayerState state);

It is important to send as little information as possible to reduce the network traffic hence we really only want to send the changes ( for example if rotation remained the same we dont send it but we do send the new position for comparison )

var previousState = new NetworkPlayerState(){ .... }
var newState = new NetworkPlayerState(previousState ){ Position= new Vector3( x, y, z ) }

NetworkPlayerState? changedState = newState .GetChangedStateComparedTo(previousState);
// null means no changes between the states and they dont need to be sent
// If you still want to send simply send new new NetworkPlayerState(){ TickNumer=currentTick }

3. Ability to duplicate with overrides

NetworkPlayerState newState= new NetworkPlayerState().OverrideWith(NetworkPlayerState overrides);

This is crucial when working with only changes and is meant to allow for cloning previous state with the received changes in a compact manner.

var lastState = new NetworkPlayerState(){ .... }
var changes= new NetworkPlayerState(){ Position= new Vector3( x, y, z ) }

NetworkPlayerState nextState = lastState.OverrideWith(changes);

This is particularly usefull to reduce the code size when sending the changes over network

Fields:

• Int TickNumber - mutable int of 11bits ( 0-2047 ) that contains the tick the state happened on the client
  It is required before sending as it is a part of the header
• bool IsParentSet - Signifies if there was a change in the parent ( null will mean unset if IsParentSet is true )
• NetworkIdentity? Parent - NetworkIdentity of the parent, it is important to know that to distinguish between no change and no parent please use new NetworkPlayerState().IsParentSet
• Vector3? Position - Player position in the world
• Vector3? BaseVelocity - Player velocity vector
• Quaternion? Rotation- Player rotation Quaternion
• byte[]? AdditionalState - Any additional state required for the game to run, they are compared as a byte array and if any byte is different will be sent

note: If parent is sent It is the developer decision if to send relative values or absolute ones

Usage example:

 [Command(requiresAuthority)]
   private void onStateChange(NetworkPlayerState clientStateChange) {
       // Add changes on top of last known State stored on the server
       nextState = lastReceivedState.OverrideWith(clientStateChange)
       lastReceivedState = nextState; // keep track of State
   }
   
   public void FixedUpdate() {
     // Send only the State changes from the client
     if (isClient) { 
       NetworkPlayerStats newState = GetPlayerState();
       NetworkPlayerState? changes = newState.GetChangedStateComparedTo(lastState)
       // only send if there is atleast 1 change ( excluding tick number )
       if (changes is not null) { 
           changes.TickNumber = currentClientTick;
           onStateChange(changes.Value);
      }
       lastState = newState;
       // Do client logic
     }
     
     if (isServer) {
        if (nextState is null) { // duplicate last knownState if no new State were sent
           nextState = new NetworkPlayerState(lastReceivedState) {
               TickNumber = currentTick; // update the tick to current;
           }
           // Do server logic
        }    
     }
   }

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Byte Structure Diagram

Summary i guess...

This is 2 of 2 structs i want to introduce to allow for a simple and coherent exchange of inputs and states between server and client.
When combined the message with both NetworkPlayerInputs and NetworkPlayerState:

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The ideal scenario is to send only the inputs on change
and every Nth tick to send inputs with the state attached for desync detection