PROJECT IS CURRENTLY (mostly) UNMAINTAINED;

L4D2 Survivor Bot AI Improver

A SourceMod plugin for Left 4 Dead 2 that tries to improve the behavior of Survivor Bots as much as possible without giving them a huge cheat-like advantages

Notable features

Bots now properly approach their melee target and switch between normal swings and bashing + ability for them to use chainsaws.
Bots can now pickup and use Tier 3 weapons without having to modify weapon scripts via plugin and etc.
You can set the weapon preferences for each survivor type (Coach, Zoey, etc.) using the "l4d2_improvedbots_weaponpreference*" convars in the plugin's config.
Improved and configurable item scavenging system
Bots now avoid moving through areas that are covered in spit or fire and try to find another way to get to their destination. They also react faster to getting spit under them and escape much efficiently.
Bots try to dodge the chargin' chargers and tank's rock that are thrown at them.
Bots now will deploy ammopacks if they have any primary weapon and defib dead survivors if they can
Bots shouldn't now completely ignore targets that are directly behind them and shoot at witch's feet at close range.
If the optional plugin is enabled, bots shouldn't now try to save a survivor if tanks are near them
Bots can now throw grenades at huge mob and tanks.
And many other features...

Requirements

MetaMod:Source 1.11 or higher: https://www.sourcemm.net/downloads.php?branch=stable
SourceMod 1.11 or higher: https://www.sourcemod.net/downloads.php?branch=stable
Left 4 DHooks Direct: https://forums.alliedmods.net/showthread.php?t=321696
Actions (Optional - Fixes bots always rushing to save their incapped friend or stopping to retreat in tank battle ): https://forums.alliedmods.net/showpost.php?p=2771520&postcount=1

Installation

Download the files in the Requirements section;
Extract the files from SourceMod and MetaMod's archives inside your game folder (Ex. C:\Program Files (x86)\Steam\steamapps\common\Left 4 Dead 2\left4dead2);
Extract the "sourcemod" folder from Left 4 DHooks Direct inside the "addons" folder;
If you chose to install Actions, extract the folders inside the archive to the "addons/sourcemod/" folder;
Download the zip file of this repository;
Put the "gamedata", "plugins", and "scripting" folders inside "addons/sourcemod".

Configuration Settings

Config file is created after starting any campaign with plugin enabled at least once and is located in "(Game installation path)/left4dead2/cfg/sourcemod/l4d2_improved_bots.cfg"

// If survivor bot shouldn't drop his currently carrying prop no matter what.
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d2_improvedbots_alwayscarryprop "1"

// Makes survivor bots automatically shove every nearby infected. <0: Disabled, 1: All infected, 2: Only if infected is behind them>
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "2.000000"
l4d2_improvedbots_autoshove_enabled "1"

// Makes survivor bots change their grenade type if there's too much of the same one, Ex. Pipe-Bomb to Molotov.
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d2_improvedbots_changeweaponiftoomanysubtype_grenades "1"

// Makes survivor bots change their primary weapon subtype if there's too much of the same one, Ex. change AK-47 to M16 or SPAS-12 to Autoshotgun.
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d2_improvedbots_changeweaponiftoomanysubtype_primaries "1"

// Enables survivor bots's charger dodging behavior.
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d2_improvedbots_chargerevasion "1"

// Range at which survivor's dead body should be for bot to consider it reviveable.
// -
// Default: "2000"
// Minimum: "0.000000"
l4d2_improvedbots_defib_revive_distance "2000"

// Enable bots reviving dead players with defibrillators if they have one available.
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d2_improvedbots_defib_revive_enabled "1"

// If bots should deploy their upgrade pack when available and not in combat.
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d2_improvedbots_deployupgradepacks "1"

// If bots shouldn't switch to their pistol while they have sniper rifle equiped.
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d2_improvedbots_dontswitchtopistol "1"

If bots should take cover from tank's thrown rocks.
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d2_improvedbots_takecoverfromtankrocks "1"

// If bots should avoid and retreat from tanks that are nearby punchable props like cars.
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d2_improvedbots_avoidtanksnearpunchableprops "1"

// Enables survivor bots' improved spitter acid evasion
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d2_improvedbots_evadespitteracids "1"

// The field of view of survivor bots.
// -
// Default: "60.0"
// Minimum: "0.000000"
// Maximum: "180.000000"
l4d2_improvedbots_vision_fieldofview "60.0"

// The time required for bots to notice enemy target is multiplied to this value.
// -
// Default: "1.0"
// Minimum: "0.000000"
// Maximum: "4.000000"
l4d2_improvedbots_vision_noticetimescale "1.0"

// Chance at which survivor bot may shove after firing a bolt-action sniper rifle. <0: Disabled, 1: Always>
// -
// Default: "3"
// Minimum: "0.000000"
l4d2_improvedbots_fireshove_chance_css_sniperrifles "3"

// Chance at which survivor bot may shove after firing a pump-action shotgun. <0: Disabled, 1: Always>
// -
// Default: "4"
// Minimum: "0.000000"
l4d2_improvedbots_fireshove_chance_pumpshotguns "4"

// Enables survivor bots throwing grenades.
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d2_improvedbots_grenadethrowing_enabled "1"

// What grenades should survivor bots throw? <1: Pipe-Bomb, 2: Molotov, 4: Bile Bomb. Add numbers together.>
// -
// Default: "7"
// Minimum: "1.000000"
// Maximum: "7.000000"
l4d2_improvedbots_grenadethrowing_grenadetypes "7"

// Infected count required to throw grenade Multiplier (Value * SurvivorCount).
// -
// Default: "3.75"
// Minimum: "1.000000"
l4d2_improvedbots_grenadethrowing_horde_size_multiplier "3.75"

// Second number to pick to randomize next grenade throw time.
// -
// Default: "30"
// Minimum: "0.000000"
l4d2_improvedbots_grenadethrowing_next_throw_time_max "30"

// First number to pick to randomize next grenade throw time.
// -
// Default: "20"
// Minimum: "0.000000"
l4d2_improvedbots_grenadethrowing_next_throw_time_min "20"

// Range at which target needs to be for bot to throw grenade at it.
// -
// Default: "1000"
l4d2_improvedbots_grenadethrowing_throw_range "1000"

// Makes survivor bots force attack pinned survivor's SI if possible. <0: Disabled, 1: Shoot at attacker, 2: Shove the attacker if close enough. Add numbers together.>
// -
// Default: "3"
// Minimum: "0.000000"
// Maximum: "3.000000"
l4d2_improvedbots_help_pinnedfriend_enabled "3"

// Range at which bots will start firing at SI.
// -
// Default: "2000"
// Minimum: "0.000000"
l4d2_improvedbots_help_pinnedfriend_shootrange "2000"

// Range at which bots will start to bash SI.
// -
// Default: "75"
l4d2_improvedbots_help_pinnedfriend_shoverange "75"

// Enable improved bot item scavenging for specified items. <0: Disable, 1: Pipe Bomb, 2: Molotov, 4: Bile Bomb, 8: Medkit, 16: Defibrillator, 32: UpgradePack, 64: Pain Pills, 128: Adrenaline, 256: Laser Sights, 512: Ammopack, 1024: Ammopile, 2048: Chainsaw
// -
// Default: "16383"
// Minimum: "0.000000"
// Maximum: "16383.000000"
l4d2_improvedbots_itemscavenge_enabled "16383"

// The bots' scavenge distance is multiplied to this value when there's no human players left in the team.
// -
// Default: "3.0"
// Minimum: "0.000000"
l4d2_improvedbots_itemscavenge_nohumans_rangemultiplier "3.0"

// Distance at which item should be for bot to able to pick it up.
// -
// Default: "96"
// Minimum: "0.000000"
l4d2_improvedbots_itemscavenge_pickup_distance "96"

// Distance at which item should be for bot to move it.
// -
// Default: "300"
// Minimum: "0.000000"
l4d2_improvedbots_itemscavenge_scavenge_distance "300"

// Distance at which a visible item should be for bot to move it.
// -
// Default: "600"
// Minimum: "0.000000"
l4d2_improvedbots_itemscavenge_scavenge_visible_distance "600"

// If bots shouldn't stop moving in combat when there's no human players in team.
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d2_improvedbots_keepmovingincombat "1"

// Range at which bot's target should be to start taking aim at it.
// -
// Default: "125"
// Minimum: "0.000000"
l4d2_improvedbots_melee_aim_range "125"

// Range at which bot's target should be to approach it. <0: Disable Approaching>
// -
// Default: "500"
// Minimum: "0.000000"
l4d2_improvedbots_melee_approach_range "500"

// Range at which bot's target should be to start attacking it.
// -
// Default: "70"
// Minimum: "0.000000"
l4d2_improvedbots_melee_attack_range "70"

// The total number of chainsaws allowed on the team. <0: Bots never use chainsaw>
// -
// Default: "1"
// Minimum: "0.000000"
l4d2_improvedbots_melee_chainsaw_limit "1"

// The nearby infected count required for bot to switch to chainsaw.
// -
// Default: "6"
// Minimum: "1.000000"
l4d2_improvedbots_melee_chainsaw_switch_count "6"

// Enables survivor bots' improved melee behaviour.
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d2_improvedbots_melee_enabled "1"

// The total number of melee weapons allowed on the team. <0: Bots never use melee>
// -
// Default: "1"
// Minimum: "0.000000"
l4d2_improvedbots_melee_max_team "1"

// Chance for bot to bash target instead of attacking with melee. <0: Disable Bashing>
// -
// Default: "4"
// Minimum: "0.000000"
l4d2_improvedbots_melee_shove_chance "4"

// The nearby infected count required for bot to switch to their melee weapon.
// -
// Default: "3"
// Minimum: "1.000000"
l4d2_improvedbots_melee_switch_count "3"

// Range at which bot's target should be to switch to melee weapon.
// -
// Default: "300"
// Minimum: "0.000000"
l4d2_improvedbots_melee_switch_range "300"

// Bots' data computing time delay (infected count, nearby friends, etc). Increasing the value might help increasing the game performance, but slow down bots.
// -
// Default: "0.1"
// Minimum: "0.033000"
l4d2_improvedbots_process_time "0.1"

// Enables survivor bots shooting tank's thrown rocks.
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d2_improvedbots_shootattankrocks_enabled "1"

// Range at which rock needs to be for bot to start shooting at it.
// -
// Default: "1500"
// Minimum: "0.000000"
l4d2_improvedbots_shootattankrocks_range "1500"

// If bots should change their primary weapon to other one if they're using CSS weapons.
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d2_improvedbots_switchoffcssweapon "1"

// Enables survivor bots' improved target selection.
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d2_improvedbots_targetselection_enabled "1"

// If bots shouldn't target common infected that are currently not attacking survivors.
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d2_improvedbots_targetselection_ignoredociles "1"

// Range at which target need to be for bots to start firing at it.
// -
// Default: "2000"
// Minimum: "0.000000"
l4d2_improvedbots_targetselection_shootrange "2000"

// Range at which target need to be for bots to start firing at it with secondary weapon.
// -
// Default: "1500"
// Minimum: "0.000000"
l4d2_improvedbots_targetselection_shootrange_pistol "1500"

// Range at which target need to be for bots to start firing at it with shotgun.
// -
// Default: "750"
// Minimum: "0.000000"
l4d2_improvedbots_targetselection_shootrange_shotgun "750"

// Range at which target need to be for bots to start firing at it with sniper rifle.
// -
// Default: "3000"
// Minimum: "0.000000"
l4d2_improvedbots_targetselection_shootrange_sniperrifle "3000"

// The total number of grenade launchers allowed on the team. <0: Bots never use grenade launcher>
// -
// Default: "1"
// Minimum: "0.000000"
l4d2_improvedbots_tier3weaponlimit_grenadelauncher "1"

// The total number of M60s allowed on the team. <0: Bots never use M60>
// -
// Default: "1"
// Minimum: "0.000000"
l4d2_improvedbots_tier3weaponlimit_m60 "1"

// Bot Bill's weapon preference. <0: Default, 1: Assault Rifle, 2: Shotgun, 3: Sniper Rifle, 4: SMG, 5: Secondary Weapon>
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "5.000000"
l4d2_improvedbots_weapon_preference_bill "1"

// Bot Coach's weapon preference. <0: Default, 1: Assault Rifle, 2: Shotgun, 3: Sniper Rifle, 4: SMG, 5: Secondary Weapon>
// -
// Default: "2"
// Minimum: "0.000000"
// Maximum: "5.000000"
l4d2_improvedbots_weapon_preference_coach "2"

// Bot Ellis's weapon preference. <0: Default, 1: Assault Rifle, 2: Shotgun, 3: Sniper Rifle, 4: SMG, 5: Secondary Weapon>
// -
// Default: "3"
// Minimum: "0.000000"
// Maximum: "5.000000"
l4d2_improvedbots_weapon_preference_ellis "3"

// Bot Francis's weapon preference. <0: Default, 1: Assault Rifle, 2: Shotgun, 3: Sniper Rifle, 4: SMG, 5: Secondary Weapon>
// -
// Default: "2"
// Minimum: "0.000000"
// Maximum: "5.000000"
l4d2_improvedbots_weapon_preference_francis "2"

// Bot Louis's weapon preference. <0: Default, 1: Assault Rifle, 2: Shotgun, 3: Sniper Rifle, 4: SMG, 5: Secondary Weapon>
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "5.000000"
l4d2_improvedbots_weapon_preference_louis "1"

// If every survivor bot should only use magnum instead of regular pistol if possible.
// -
// Default: "0"
// Minimum: "0.000000"
// Maximum: "1.000000"
l4d2_improvedbots_weapon_preference_magnums_only "0"

// Bot Nick's weapon preference. <0: Default, 1: Assault Rifle, 2: Shotgun, 3: Sniper Rifle, 4: SMG, 5: Secondary Weapon>
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "5.000000"
l4d2_improvedbots_weapon_preference_nick "1"

// Bot Rochelle's weapon preference. <0: Default, 1: Assault Rifle, 2: Shotgun, 3: Sniper Rifle, 4: SMG, 5: Secondary Weapon>
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "5.000000"
l4d2_improvedbots_weapon_preference_rochelle "1"

// Bot Zoey's weapon preference. <0: Default, 1: Assault Rifle, 2: Shotgun, 3: Sniper Rifle, 4: SMG, 5: Secondary Weapon>
// -
// Default: "3"
// Minimum: "0.000000"
// Maximum: "5.000000"
l4d2_improvedbots_weapon_preference_zoey "3"

// Allows survivor bots to crown witch on their path if they're holding any shotgun type weapon. <0: Disabled; 1: Only if survivor team doesn't have any human players; 2:Enabled>
// -
// Default: "1"
// Minimum: "0.000000"
// Maximum: "2.000000"
l4d2_improvedbots_witchbehavior_allowcrowning "1"

// Survivor bots will start walking near witch if they're this range near her and she's not disturbed. <0: Disabled>
// -
// Default: "500"
// Minimum: "0.000000"
l4d2_improvedbots_witchbehavior_walkwhennearby "500"