Getting Started
Basic knowledge of C# and Unity is required.
Setting Up Your Environment
Connecting Unity to your editor
Make sure your Unity Editor is connected to whatever you're using to write the script. (Example: Visual Studio Community)
In the Unity Editor, click Edit -> Preferences -> External Tools -> External Script Editor -> Visual Studio Community.
Restart both your Unity Editor and your Script Editor to make sure these changes take affect.
Creating your mod
Create a new mod and name it whatever your script does.
In the Unity Editor click Holdfast SDK Tools -> Create Empty Mod
In this mod’s folder create a new script and name it what you named your mod.
Double click the script in your Unity Project to open it.
Core Concepts
Shared Interface
The script should implement the shared interface that you're going to be using. Each interface has a few different functions but operates the same.
IHoldfastGame, IHoldfastSharedMethods, IHoldfastSharedMethods2, IHoldfastSharedMethods3.
- If you're using multiple IHoldfastSharedMethods, make sure you implement them together at the top of your script.
Example: public class LineFormer : IHoldfastSharedMethods, IHoldfastSharedMethods2, IHoldfastSharedMethods3
Example: Here’s a mod that’s called “LineFormer” that has the script called “LineFormer.cs” which implements the IHoldfastSharedMethods interface.
Example 2: Here’s a mod that’s called “MeleeTrainer” that has the script called “MeleeTrainer.cs” which implements the IHoldfastSharedMethods & IHoldfastSharedMethods2 interfaces.
Client or Server, what are those?!
One of the most important concepts to understand while script modifying Holdfast is the concept of "Client" and "Server".
The "Server" is the game server which handles all players verification data, networking, chat/voip, etc.
Whereas the "Client" is either your own client referred to as the "Owner/Local Player" or someone else referred to as a "Proxy".
Mod Install and Load Types
Similarly to the normal process of using the load_mod <steam_id> load type for mods, we've added a load_mod_server_only <steamid> which loads a mod specifically only on server side (such as a custom stats tracking or auto admin mod), and a load_mod_client_only <steamid> which inversely only loads the mod on client side (such as a ui mod or a audio replacement mod). In addition mods_installed_server_only <steamid> was also added. The advantage of this is mods that the client does not need to join the server, the clients won't need to install the mod on their end.
The load order for this new feature is first all the Common Mods are loaded and than the client/server specific one's are loaded. As always, the internal order of each list, is dependent on the order of how they were typed in the config file.
Please note players can only load mods that the server allows on their list, so a mods_installed_client_only <steamid> doesn't make sense, so if you're going to be making a client only loaded mod, it needs to be installed on both the client and the server.
Mod Variables
Simply put, mods can receive variables through the PassConfigVariables() method. These variables are supplied in the server config file in the format mod_variable <string> for Global Scope (outside of the map rotations) or mod_variable_local <string> for Local Scope (inside the map rotation). Global Scope variables will always be loaded BEFORE any local scope variables.
Server config mod variables are sent to all mods running on the server. To prevent conflicts where one mod accidentally reads another mod's settings, it is highly recommended to prefix your variables. A common and effective pattern is modID:key:value, where modID is a unique identifier for your mod (like its Steam Workshop ID or a custom prefix).
Practical Example: Slay Players on Spawn
Part 1: The Mod_Variable
mod_variable HardcoreMod:EnableKillOnSpawn:true
HardcoreMod: This is the modID.EnableKillOnSpawn: This is the key.True: This is the value.
Part 2: Script Implementation
- This script would parse this variable and use its value. This example shows how to safely check for your mod's specific variable and convert the text "true" into a boolean
true.
Security Concerns
As you might be aware, we have some security related scripts that, for example don't allow a modder to gain access to the server or client's machine (ie: System.IO, System.Reflection, etc), these typically will show up as an error on the server's console with something along the lines of
[UMod.Scripting.ScriptDomain]: Illegal reference to disallowed namespace: System.Reflection.
We've added a feature for server hosts to be able to pass a "-allowRestrictedMods" in the launch parameters of the server. This will turn off the securities on the server machine ONLY, for ALL the mods. As such, if you rent your servers, you will need to talk to your host provider to enable this if they want to support it.
What this will allow you to do is hook directly with IO operations and other restricted features (writing files, databases, websites api's, etc) so for development this will open major features that will be able to be done easier or that weren't able to be done outright.
Gotchya's
It's highly recommended that most actions that a mod would do would be defered by a frame or a few ms when it comes to interacting with a player (healing, damaging, reviving, positioning, rotation, etc). If you code something, and it's logically sound, but ingame it's not doing exactly as expected or has bugs occuring due to it, after trying to delay the action, feel free to ask in mod-support.
Note, don't use a "static" member inside of the Interface classes. This confuses the dynamic loader of C# and it'll be bad times for you trying to figure out why.
RC commands specific for modding use
Make carbon player bots not do any auto input
If you plan on modifying bots position or rotation, call the following script to force bots to not auto move or rotate. Note: this is different than setting the carbonplayer forceInputAxis/forceInputRotation, since thoses ones will lock ALL the bots in the action, whereas this will allow you to individually control bots's facing rotation and movement system.
rc carbonPlayers ignoreAutoControls <true/false>
Send network trajectory info to client without showing it to players
Similar to drawFirearmTrajectories, this will send the trajectory data from server to client. Unlike the aforementioned command, this will NOT display it to the player, but the mod will still be recieving the data. Enable this only if you're planning on using the "OnShotInfo" on a client side, for server side mods, this isn't required.
rc set drawFirearmTrajectoriesInfo <true/false>
Quiet Messages: Server-to-Client Data Transfer
Quiet messages are a powerful tool for a server-side mod to send data to a client-side mod without showing anything in the player's chat. They are essential for any mod where the server needs to update a client's custom UI or trigger a client-side action.
- The communication flow is simple:
- The server executes an rc command to send a string of data.
- The client receives that string from the OnTextMessage event.
Sending Data from the Server
- Use one of the following commands:
rc serverAdmin quietPrivateMessage <player_id> <message>
rc serverAdmin quietBroadcastMessage <message>
Receiving Data on The Client
- Your client-side mod will receive the data in the OnTextMessage method. It's crucial to filter these messages to ensure you only process the ones intended for your mod.
- Because OnTextMessage can be used by many different mods simultaneously, you must create a unique message format to avoid conflicts. If you don't, your mod might try to process messages from another mod, leading to errors. A highly recommended pattern is to prefix your messages with a unique ID, like:
MOD_ID:COMMAND:VALUE.
Practical Example: Welcome Message to a Debug.Log
Part 1: The Server-Side Code (Sending the Message) -
- This code runs on the server. When a player spawns, it sends them a quiet message containing their own PlayerID.
Part 2: The Client-Side Code (Receiving the Message)
- This code runs on every client. It listens for the specific welcome message and logs it.
IHoldfastGame
To execute RC commands from your script you must gain access one of the game's core methods. This is accomplished by implementing the "IHoldfastGame" interface.
Implement the Interface
- First, ensure your script is using the HoldfastBridge namespace.
- Your main class signature must then use IHoldfastGame.
Receive and Store the Game Methods
- The IHoldfastGame interface requires you to implement the OnGameMethodsInitialized method. The game engine calls this method once during startup and provides an IHoldfastGameMethods object.
- The best practice is to store this object in a static property. This makes the game methods accessible from anywhere in your mod's codebase without needing to pass references around.
Execute a Command
- With the GameMethods stored, you can now call ExecuteConsoleCommand from any part of your mod.
void ExecuteConsoleCommand(string command, out string output, out bool success);
command: The RC command string to execute.output: An out parameter that will be filled with any text the command returns. This is very useful for debugging.success: An out parameter that will be true if the command was recognized and executed successfully.
Practical Example: Toggling Mouse Lock for a UI Panel
- This is a common use case. When you show a custom UI, you might want to unlock the mouse to the player can interact with it.
IHoldfastSharedMethods
If you hover over the interface's properties in visual studio, these can be found in the inspector too. In case visual studio doesn't link the dll correctly to inspect the data, feel free to refer to the raw cs files inside the DLL.
OnSyncValueState
The game will share an int when the mod loads. A random synchronized value (same on client and server), for example useful if you need a seed for a map generator.
void OnSyncValueState(int value);
OnUpdateSyncedTime
The game will share the current synchronized time (same on client and server) on every frame of the game.
void OnUpdateSyncedTime(double time);
OnUpdateElapsedTime
The game will return the seconds since the round started on every frame of the game.
void OnUpdateElapsedTime(float time);
OnUpdateTimeRemaining
The game will share the current remaining time on every frame of the game.
void OnUpdateTimeRemaining(float time);
OnIsServer
The game will return if the mod is loaded on a server.
void OnIsServer(bool server);
OnIsClient
The game will return if the mod is loaded on a client, if it is, you'll retrieve the current player's steam id.
void OnIsClient(bool client, ulong steamId);
OnRoundDetails
The game will call this on round start with details regarding the current round.
void OnRoundDetails(int roundId, string serverName, string mapName, FactionCountry attackingFaction, FactionCountry defendingFaction, GameplayMode gameplayMode, GameType gameType);
PassConfigVariables
The game will call this once with all the config variables set on the config file of the server.
Note: you will receive all variables, so make sure to filter only the ones you care about.
void PassConfigVariables(string[] value);
OnPlayerJoined
The game will call this when a player or a bot joins the round.
void OnPlayerJoined(int playerId, ulong steamId, string name, string regimentTag, bool isBot);
OnPlayerLeft
The game will call this when a player leaves the round.
Note: Bots cannot leave, they'll keep respawning once dead.
void OnPlayerLeft(int playerId);
OnPlayerSpawned
The game will call this when a player spawns in game.
void OnPlayerSpawned(int playerId, int spawnSectionId, FactionCountry playerFaction, PlayerClass playerClass, int uniformId, GameObject playerObject);
OnPlayerHurt
The game will call this when a player is hurt in game.
void OnPlayerHurt(int playerId, byte oldHp, byte newHp, EntityHealthChangedReason reason);
OnPlayerKilledPlayer
The game will call this when a player is killed by another player.
void OnPlayerKilledPlayer(int killerPlayerId, int victimPlayerId, EntityHealthChangedReason reason, string details);
OnScorableAction
The game will call this when a player receives any score.
void OnScorableAction(int playerId, int score, ScorableActionType reason);
OnPlayerShoot
The game will call this when a player shoots his gun.
void OnPlayerShoot(int playerId, bool dryShot);
OnShotInfo
The game will call this when a bullet.
Note: This requires `rc set drawFirearmTajectories true` or `rc set drawFirearmTajectoriesInfo true`.
void OnShotInfo(int playerId, int shotCount, Vector3[][] shotsPointsPositions, float[] trajectileDistances, float[] distanceFromFiringPositions, float[] horizontalDeviationAngles, float[] maxHorizontalDeviationAngles, float[] muzzleVelocities, float[] gravities, float[] damageHitBaseDamages, float[] damageRangeUnitValues, float[] damagePostTraitAndBuffValues, float[] totalDamages, Vector3[] hitPositions, Vector3[] hitDirections, int[] hitPlayerIds, int[] hitDamageableObjectIds, int[] hitShipIds, int[] hitVehicleIds);
OnPlayerBlock
The game will call this when a player successfully blocks another player.
void OnPlayerBlock(int attackingPlayerId, int defendingPlayerId);
OnPlayerMeleeStartSecondaryAttack
The game will call this when a player starts a secondary attack (shove).
void OnPlayerMeleeStartSecondaryAttack(int playerId);
OnPlayerWeaponSwitch
The game will call this when a player swaps their weapon.
void OnPlayerWeaponSwitch(int playerId, string weapon);
OnPlayerStartCarry
The game will call this when a player starts carrying an object.
void OnPlayerStartCarry(int playerId, CarryableObjectType carryableObject);
OnPlayerEndCarry
The game will call this when a player stops carrying an object.
void OnPlayerEndCarry(int playerId);
OnPlayerShout
The game will call this when a player shouts using the ingame voice commands(not voip).
void OnPlayerShout(int playerId, CharacterVoicePhrase voicePhrase);
OnConsoleCommand
The game will call this when the console command is used.
Note: This will be only called on the client, or on the server that is executing the console command.
void OnConsoleCommand(string input, string output, bool success);
OnRCLogin
The game will call this when a player requests a remote console login.
Note: This will be called on the client that is executing the request, and the server. Not other people.
void OnRCLogin(int playerId, string inputPassword, bool isLoggedIn);
OnRCCommand
The game will call this when a player requests a remote console command.
Note: This will be called on the client that is doing the request, and the server. Not other people.
void OnRCCommand(int playerId, string input, string output, bool success);
OnTextMessage
The game will call this when a message is received in the chat system.
void OnTextMessage(int playerId, TextChatChannel channel, string text);
OnAdminPlayerAction
The game will call this when an administrator does an admin action using the rc commands or the P menu.
void OnAdminPlayerAction(int playerId, int adminId, ServerAdminAction action, string reason);
OnDamageableObjectDamaged
The game will call this when an object is damaged.
void OnDamageableObjectDamaged(GameObject damageableObject, int damageableObjectId, int shipId, int oldHp, int newHp);
OnInteractableObjectInteraction
The game will call this when an object is interacted with.
void OnInteractableObjectInteraction(int playerId, int interactableObjectId, GameObject interactableObject, InteractionActivationType interactionActivationType, int nextActivationStateTransitionIndex);
OnEmplacementPlaced
The game will call this when an emplacement (sapper object) is initially placed.
void OnEmplacementPlaced(int itemId, GameObject objectBuilt, EmplacementType emplacementType);
OnEmplacementConstructed
The game will call this when an emplacement (sapper object) is fully constructed.
void OnEmplacementConstructed(int itemId);
OnCapturePointCaptured
The game will call this when a capture point is fully captured.
void OnCapturePointCaptured(int capturePoint);
OnCapturePointOwnerChanged
The game will call this when a capture point changes owner.
void OnCapturePointOwnerChanged(int capturePoint, FactionCountry factionCountry);
OnCapturePointDataUpdated
The game will call this when a capture data changes.
void OnCapturePointDataUpdated(int capturePoint, int defendingPlayerCount, int attackingPlayerCount);
OnBuffStart
The game will call this when a buff is applied to a player.
Note: Buffs that already exist on a player may stack, so this call will be called multiple times even if a player already has the buff.
void OnBuffStart(int playerId, BuffType buff);
OnBuffStop
The game will call this when a buff is removed from a player.
void OnBuffStop(int playerId, BuffType buff);
OnRoundEndFactionWinner
The game will call this when a faction vs faction round is over.
Note: Most of them except for Army Deathmatch.
void OnRoundEndFactionWinner(FactionCountry factionCountry, FactionRoundWinnerReason reason);
OnRoundEndPlayerWinner
The game will call this when a free for all round is over.
Note: Only Army Deathmatch.
void OnRoundEndPlayerWinner(int playerId);
OnVehicleSpawned
The game will call this when a vehicle(horse) is spawned.
void OnVehicleSpawned(int vehicleId, FactionCountry vehicleFaction, PlayerClass vehicleClass, GameObject vehicleObject, int ownerPlayerId);
OnVehicleHurt
The game will call this when a vehicle(horse) is hurt.
void OnVehicleHurt(int vehicleId, byte oldHp, byte newHp, EntityHealthChangedReason reason);
OnPlayerKilledVehicle
The game will call this when a vehicle(horse) is killed by a player.
void OnPlayerKilledVehicle(int killerPlayerId, int victimVehicleId, EntityHealthChangedReason reason, string details);
OnShipSpawned
The game will call this when a ship is spawned.
void OnShipSpawned(int shipId, GameObject shipObject, FactionCountry shipfaction, ShipType shipType, int shipName);
OnShipDamaged
The game will call this when a ship takes damage.
void OnShipDamaged(int shipId, int oldHp, int newHp);
IHoldfastSharedMethods2
OnPlayerPacket
This will be called every time we get a packet from a user.
Note: Server Side ONLY.
void OnPlayerPacket(int playerId, byte? instance, Vector3? ownerPosition, double? packetTimestamp, Vector2? ownerInputAxis, float? ownerRotationY, float? ownerPitch, float? ownerYaw, PlayerActions[] actionCollection, Vector3? cameraPosition, Vector3? cameraForward, ushort? shipID, bool swimming);
OnVehiclePacket
This will be called every time we get a packet from a vehicle.
Note: Server Side ONLY.
void OnVehiclePacket(int vehicleId, Vector2 inputAxis, bool shift, bool strafe, PlayerVehicleActions[] actionCollection);
OnOfficerOrderStart
This will be called every time we get a officer order.
void OnOfficerOrderStart(int officerPlayerId, HighCommandOrderType officerOrderType, Vector3 orderPosition, float orderRotationY, int voicePhraseRandomIndex);
OnOfficerOrderStop
This will be called every time we get a officer order stop.
void OnOfficerOrderStop(int officerPlayerId, HighCommandOrderType officerOrderType);
IHoldfastSharedMethods3
OnStartSpectate
This will be called when a player starts spectating someone else.
void OnStartSpectate(int playerId, int spectatedPlayerId);
OnStopSpectate
This will be called when a player stops spectating.
void OnStopSpectate(int playerId, int spectatedPlayerId);
OnStartFreeflight
This will be called when a player starts using freeflight cam.
void OnStartFreeflight(int playerId);
OnStopFreeflight
This will be called when a player stops using freeflight cam.
void OnStopFreeflight(int playerId);
OnMeleeArenaRoundEndFactionWinner
This will be called on a melee arena round end depending on who wins the round.
void OnMeleeArenaRoundEndFactionWinner(int roundId, bool attackers);
OnPlayerConnected
This will be called when a player connects to a server.
This is the normal flow: OnPlayerConnected -> tell the player to loading screen -> player picks faction+class -> OnPlayerJoined
Note: Server Only.
void OnPlayerConnected(int playerId, bool isAutoAdmin, string backendId);
OnPlayerDisconnected
This will be called when a player leaves a server.
Unlike OnPlayerLeave, this happens even on people that didn't spawn in
Note: Server Only.
void OnPlayerDisconnected(int playerId);
SharedMethods Copy/Paste
Here is a file that has all the SharedMethods in a single file so you can copy paste them easily.
https://github.com/Xarkanoth/Holdfast-Scripts/tree/main/IHoldfastSharedMethods
Key Scene GameObjects
When developing client-side mods, you will often need to find and interact with specific GameObjects that are part of the game's scene. Knowing the names of these objects and how to access them is essential for tasks like creating custom UI and manipulating cameras.
Note: GameObject names can change at any time with no update regarding the name change.
The Main Camera: Main Camera SCENE
This is the primary camera that renders the player's view. You might interact with it to get its position, change its field of view, or attach custom visual effects.
- Name:
Main Camera SCENE
- Example: Finding the Main Camera
The Main UI Canvas: Main Canvas
This GameObject is the root of most of Holdfast's user interface. If you want to add your own UI elements (like panels, text, or images), you will typically make them children of this canvas to ensure they are rendered correctly on the player's screen.
- Name:
Main Canvas
- Example: Finding the Main Canvas
ClientScene GameObjects
{
