Mutation Gametype (L4D2)

Introduction

With the "Expanded Mutation System" update, game modes are now handled via individual gamemode definition files. This gives a convenient way to create additional game mode entries that are based off the main four: coop, realism, versus, and scavenge, as well as brand new modes with advanced custom scripting.

Legacy mutations using the L4D2 Gamemodes File gamemodes.txt can still be used, but only one add-on can be active at a time.

Important aspects of mutations:

• A mutation is a modified game mode that mainly consists of modified cvars and a mutation vscript.
• A mutation name is the game mode entry name set in the mode definition file.
• All mutations can be loaded via the main menu GUI, but can also be loaded via console map <map name> <game mode name> Examples: map c1m1_hotel mutation13 or map c1m1_hotel survival
• Cvars are placed in a game mode definition.
• A vscript of the same name (<game mode name>.nut) is also loaded to complete additional tasks. For example, it may contain a function to replace weapons. Map-specific vscripts (<mapname>_<game mode name>.nut) are also loaded.

Custom mutations

To do: discuss workflow, useful commands for development and testing

Alternate instructions: Custom Mutations Tutorial (Steam Forums)

Example game mode definition file

The definition files are added as \left 4 dead 2\left4dead2\modes\<modename>.txt

For a list of nearly all of the available cvars in L4D2, please see List of L4D2 Cvars

Note:Not all cvars will "work" and will need testing

Note:Only one mode definition is allowed per file

"my_example_mode" // Name of the game mode and also the name of the vscript that will automatically load when a game mode is started, either via console or GUI.
{
	"base"				"none" // Game mechanics are inherited from this mode. It can be coop/versus/survival/scavenge/realism or an other mutation. It can also be "none" for novel game modes.
	"maxplayers"    		"4" // Set the number of players allowed. Allowed values are 1, 4 and 8.
	"hasdifficulty"			"1" // Sets if difficulty is allowed.
	"singlechapter"			"1" // Checks if there is only one level (Used in Survival/Scavenge).
	"playercontrolledzombies"	"1" // Allows/Disallows players to control infected.
	"hasroundlimit"			"1" // Has rounds?

	// These settings control how the mode is displayed in the Mutations menu.
	"DisplayTitle"			"Example Gamemode!"
	"Description"			"An example mode to demonstrate the mutation system."
	"Author"			"Me!"
	"Image"				"vgui/my_thumbnail_material" // Normally 512 x 256 pixels
 
	// This is the part where cvars can be added to alter the game mode, this allows hidden cvars as well.
	convar 
	{ 
		pain_pills_decay_rate 0.27
		z_speed 500
	}
}

Mutation vscript examples

For all of the official mutation vscripts, along with other official vscripts, please see L4D2 Vscripts

Note:These scripts might be outdated, plese see L4D2_EMS for up-to-date examples

Chainsaw Massacre (mutation7.nut)

//-----------------------------------------------------
Msg("Activating Mutation 7\n");


DirectorOptions <-
{
	ActiveChallenge = 1

	cm_InfiniteFuel = 1
	cm_ShouldHurry = 1

	weaponsToRemove =
	{
		weapon_pistol = 0
		weapon_pistol_magnum = 0
		weapon_smg = 0
		weapon_pumpshotgun = 0
		weapon_autoshotgun = 0
		weapon_rifle = 0
		weapon_hunting_rifle = 0
		weapon_smg_silenced = 0
		weapon_shotgun_chrome = 0
		weapon_rifle_desert = 0
		weapon_sniper_military = 0
		weapon_shotgun_spas = 0
		weapon_grenade_launcher = 0
		weapon_rifle_ak47 = 0
		weapon_smg_mp5 = 0
		weapon_rifle_sg552 = 0
		weapon_sniper_awp = 0
		weapon_sniper_scout = 0
		weapon_rifle_m60 = 0
		weapon_melee = 0
		weapon_upgradepack_incendiary = 0
		weapon_upgradepack_explosive = 0
		ammo = 0
		upgrade_item = 0
	}

	function AllowWeaponSpawn( classname )
	{
		if ( classname in weaponsToRemove )
		{
			return false;
		}
		return true;
	}	

	function ShouldAvoidItem( classname )
	{
		if ( classname in weaponsToRemove )
		{
			return true;
		}
		return false;
	}	

	DefaultItems =
	[
		"weapon_chainsaw",
		"weapon_pistol",
	]

	function GetDefaultItem( idx )
	{
		if ( idx < DefaultItems.len() )
		{
			return DefaultItems[idx];
		}
		return 0;
	}	
}

removed_weapon_spawns <- false;
function Update()
{
	if( !removed_weapon_spawns )
	{
		EntFire( "weapon_spawn", "kill" );
		removed_weapon_spawns = true;
	}
}    

Headshot! (mutation2.nut)

//-----------------------------------------------------
Msg("Activating Mutation 2\n");


DirectorOptions <-
{
	ActiveChallenge = 1

	cm_HeadshotOnly = 1
}

Gib Fest (mutation14.nut)

//-----------------------------------------------------
Msg("Activating Mutation 14\n");


DirectorOptions <-
{
	ActiveChallenge = 1

	weaponsToRemove =
	{
		weapon_pistol = 0
		weapon_pistol_magnum = 0
		weapon_smg = 0
		weapon_pumpshotgun = 0
		weapon_autoshotgun = 0
		weapon_rifle = 0
		weapon_hunting_rifle = 0
		weapon_smg_silenced = 0
		weapon_shotgun_chrome = 0
		weapon_rifle_desert = 0
		weapon_sniper_military = 0
		weapon_shotgun_spas = 0
		weapon_grenade_launcher = 0
		weapon_rifle_ak47 = 0
		weapon_smg_mp5 = 0
		weapon_rifle_sg552 = 0
		weapon_sniper_awp = 0
		weapon_sniper_scout = 0
		weapon_rifle_m60 = 0
		weapon_melee = 0
		weapon_chainsaw = 0
		ammo = 0
	}

	function AllowWeaponSpawn( classname )
	{
		if ( classname in weaponsToRemove )
		{
			return false;
		}
		return true;
	}	

	DefaultItems =
	[
		"weapon_rifle_m60",
		"weapon_pistol_magnum",
	]

	function GetDefaultItem( idx )
	{
		if ( idx < DefaultItems.len() )
		{
			return DefaultItems[idx];
		}
		return 0;
	}	
}

removed_weapon_spawns <- false;
function Update()
{
	if( !removed_weapon_spawns )
	{
		EntFire( "weapon_spawn", "kill" );
		removed_weapon_spawns = true;
	}
}

See also

• Decompiled Official Vscripts
• L4D2 Gamemodes File
• L4D2 Vscript Examples
• L4D2 Vscripts
• List of L4D2 Cvars
• VScript

External links

• Custom Mutations Tutorial (Steam Forums)
• "All Mutations Unlocked" (Steam Forums)