User:Gazyi/CS:GO Bot Behavior Trees

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Counter-Strike: Global Offensive Level Creation

In Counter-Strike: Global Offensive Counter-Strike: Global Offensive, bots can be given a Behavior Tree to follow. A behavior tree dictates how the bot senses things (vision, hearing, damage sensing), moves, attacks, and does other actions.

They use Valve's proprietary KeyValues3 format (.kv3), which is a text-based format with somewhat strict syntax. They typically use the bt_ prefix, to signify that file is a Behavior Tree. They are stored in csgo/scripts/ai. One can create and use his own behavior trees, see below.

Officially, behavior trees are used for the game modes Csgo icon coopstrike.png Co-op Strike, Csgo icon guardian.png Guardian and Csgo icon deathmatch.png Deathmatch.

Behavior trees were first added to the game on September 16, 2019. Since September 1, 2020, behavior trees can be packed into BSP files.

Using a Behavior Tree

The ConVar mp_bot_ai_bt can assign a behavior tree to all bots on the server. Its value is a string representing the path to a .kv3 file, starting from csgo/. For example, the following line is used for official Deathmatch and can be found in csgo/cfg/gamemode_deathmatch.cfg:

mp_bot_ai_bt "scripts/ai/deathmatch/bt_default.kv3"

For the Co-op game mode, info_enemy_terrorist_spawn entities have the KeyValue behavior_tree_file that can be used to specify a behavior tree only for bots spawning at this entity.

Related Console Commands

ConVar Default Value Description
cv_bot_ai_bt_debug_target -1 Draw the behavior tree of the given bot.
cv_bot_ai_bt_hiding_spot_show 0 Draw hiding spots.
cv_bot_ai_bt_moveto_show_next_hiding_spot 0 Draw the hiding spot the bot will check next.
mp_bot_ai_bt "" Use the specified behavior tree file to drive the bot behavior.
mp_bot_ai_bt_clear_cache ConCommand Clears the cache for behavior tree files.

Format

The first line of a .kv3 file is always a header specifying the KV3 version. For CS:GO, use this header:

<!-- kv3 encoding:text:version{e21c7f3c-8a33-41c5-9977-a76d3a32aa0d} format:generic:version{7412167c-06e9-4698-aff2-e63eb59037e7} -->

Now define general bot configuration. Use "config" key, which should contain full path to that file, including file extension:

<!-- kv3 encoding:text:version{e21c7f3c-8a33-41c5-9977-a76d3a32aa0d} format:generic:version{7412167c-06e9-4698-aff2-e63eb59037e7} -->
{
	config = "scripts/ai/<path to bt_config>/<bt_config_name>.kv3"
}

Behavior trees always start with root. Define it with "root" key. Every behavior node should be inside it.

<!-- kv3 encoding:text:version{e21c7f3c-8a33-41c5-9977-a76d3a32aa0d} format:generic:version{7412167c-06e9-4698-aff2-e63eb59037e7} -->
{
	config = "scripts/ai/<path to bt_config>/<bt_config_name>.kv3"
	root = 
	{
		<Behavior Node>
	}
}

Behavior Node format depends on its type and parameters:

<!-- kv3 encoding:text:version{e21c7f3c-8a33-41c5-9977-a76d3a32aa0d} format:generic:version{7412167c-06e9-4698-aff2-e63eb59037e7} -->
{
	config = "scripts/ai/<path to bt_config>/<bt_config_name>.kv3"
	root = 
	{
		type = <Node Type>
		<parameter> = <value>
		...
		child = 
		{
			<Behavior Node>
		}
	}
}

Some nodes allows to define new global variables. Their input name should contain both double and single quotes:

type = "action_set_global_counter"
input_name = "'Test'" // Note those quotation marks.
input_value = 1

Configuration

To do: 

  • Explain parameters in bt_config

These parameters define general bot reaction and combat behavior for every bot skill ( low, fair, normal, tough, hard, very_hard, expert, default ), like a botprofile.db.

Default format is:

<!-- kv3 encoding:text:version{e21c7f3c-8a33-41c5-9977-a76d3a32aa0d} format:generic:version{7412167c-06e9-4698-aff2-e63eb59037e7} -->
{
	<skill level>
	{
		<Variables from table below>
		attack = <Attack table>
	}
}

List of parameters

Variable Description
aim_target_acquisition_lerp_time
aim_target_acquisition_lerp_time_deviation
aim_target_acquisition_angle_penalty
aim_target_acquisition_angle_penalty_deviation
aim_target_acquisition_angle_penalty_reduction_ratio
aim_target_acquisition_angle_tolerance
aim_target_acquisition_angle_lerp_bias
aim_target_tracking_lerp_time
aim_target_tracking_lerp_time_deviation
aim_target_tracking_focus_interval
aim_target_tracking_focus_interval_deviation
aim_target_tracking_angle_lerp_bias
aim_new_target_angle_tolerance
aim_max_duration
aim_max_duration_deviation
aim_punch_angle_reaction_chance
look_around_awareness_yaw_range Max angle to horizontal rotate viewcamera from this viewpoint.
look_around_awareness_pitch_range Max angle to vertical rotate viewcamera from this viewpoint.
look_around_focus_interval Delay between next viewcamera rotation.
look_around_focus_interval_deviation
look_around_lerp_time Time to rotate viewcamera to next position.
look_around_lerp_time_deviation
look_around_lerp_bias Smooths viewcamera movement.
reaction_time Delay before reaction on event.
combat_crouch_chance
combat_dodge_command_duration
combat_dodge_command_duration_deviation

Attack Table

Attack table defines handling of different weapon types.

Example:

attack =
[
	// duration, duration deviation, cadence, cooldown, cooldown deviation

	// KNIFE						PISTOL							SUBMACHINEGUN
	[ -1.0, -1.0, -1.0, -1.0, -1.0 ],[ 0.95, 0.25, 0.5, 0.15, 0.05 ],[ 0.42, 0.07, 0.0, 0.15, 0.05 ],
	// RIFLE						SHOTGUN							SNIPER_RIFLE
	[ 0.22, 0.07, 0.0, 0.45, 0.15 ],[ 0.3, 0.0, 0.0, 0.95, 0.25 ],[ 0.22, 0.07, 0.0, 2.0, 0.0 ],
	// MACHINEGUN					C4								TASER
	[ 0.75, 0.15, 0.0, 0.3, 0.1 ],[ -1.0, -1.0, -1.0, -1.0, -1.0 ],	[ -1.0, -1.0, -1.0, -1.0, -1.0 ],
	// GRENADE						EQUIPMENT						STACKABLEITEM
	[ -1.0, -1.0, -1.0, -1.0, -1.0 ],[ -1.0, -1.0, -1.0, -1.0, -1.0 ],[ -1.0, -1.0, -1.0, -1.0, -1.0 ],
	// FISTS						BREACHCHARGE					BUMPMINE
	[ -1.0, -1.0, -1.0, -1.0, -1.0 ],[ -1.0, -1.0, -1.0, -1.0, -1.0 ],[ -1.0, -1.0, -1.0, -1.0, -1.0 ],
	// TABLET						MELEE							SHIELD
	[ -1.0, -1.0, -1.0, -1.0, -1.0 ],[ -1.0, -1.0, -1.0, -1.0, -1.0 ],[ -1.0, -1.0, -1.0, -1.0, -1.0 ],
	// WEAPONTYPE_ZONE_REPULSOR		UNKNOWN
	[ -1.0, -1.0, -1.0, -1.0, -1.0 ],[ -1.0, -1.0, -1.0, -1.0, -1.0 ]
]

Nodes

This is a list of all nodes on November 9, 2021.

To do: 

  • Complete node parameters and descriptions, check for inaccuracies.
  • Define variable types for parameters.
  • Explain all parameters.

Combinators

Type Parameters Description
parallel Executes all child functions in one script tick.
selector Executes child functions as sequence until meeting child with true condition.
sequencer Executes child functions as sequence until meeting child with false condition.
subtree string file, string name Executes behavior tree from file.

Decorators

Type Parameters Description
decorator_bot_service array memory_to_expire(variable? domain (GroupID or AllBots), flag key (ShortTermAttackMemory, ShortTermDamageMemory, ShortTermAreaDamageMemory, ShortTermInvestigateMemory, LongTermMemory, DamageThroughSmokeMemory, Threats), int time, int distance), array tagged_entities_to_expire, int_flag? basic_chatter_enable, vector? input_chatter_enemies, int chatter_outnumbered_threshold Kinda main bot behavior function? Usually contains all subtree routines.
decorator_buy_service array output Returns array of items that bot will buy, then executes function.
decorator_dec_global_counter variable input_name Decreases input variable by 1, then executes function?
decorator_find_utility_strat vector input_location, int distance_threshold, vector output_location, vector output_angles, string output_weapon Unused.
decorator_game_event
Warning.png Warning: Release Notes for 21/10/2021 say about it but it doesn't exist in code?
decorator_hiding_spot_service variable? domain (GroupID or AllBots), vector output_hiding_spot, int distance_threshold, int expiration_time Returns hiding spot, then executes function? Usually located right after script root.
decorator_invert Unused. Valve scripts usually use negated = 1 flag in node parameters.
decorator_maybe float chance Executes child functions with specified chance (1 - 100%, 0.7 - 70% etc).
decorator_memory vector? input, memory? output, string output_domain Saves input in specified memory buffer?
decorator_need_healing int health_threshold Executes child functions if bot health is lower that input threshold.
decorator_picker_blocked_by_smoke vector? input, int distance_threshold Executes child functions if input position is behind smoke volume?
decorator_picker_dedup vector? input, memory? against, int distance_threshold ??? Only used in noise picker in Valve scripts.
decorator_picker_grenade_type array input, array types (EXPLOSIVE, FLASH, FIRE, DECOY, SMOKE, SENSOR, SNOWBALL) Executes child functions on specified grenade types.
decorator_picker_max_score array input ???
decorator_picker_nearby array input, int cutoff_distance Executes child functions if input entities are within distance.
decorator_picker_random_by_distance array input, int distance_min, int distance_max Executes child functions if random entity from input is within distance limits?
decorator_picker_reaction_time variable? input_domain (GroupID or AllBots), memory? input, vector? output Executes child functions after delay, that depends of bot skill reaction time?
decorator_picker_visible array input, int_flag? check_fov Executes function if input entity in LOS?
decorator_picker_weight_as_distance array input ??? Only used in noise picker in Valve scripts.
decorator_random_approach_point vector output Returns a random point in navmesh.
decorator_random_int int min, int max, int output Returns a random int the range of min to max.
decorator_ranker_dist array input Sorts entities depending on distance?
decorator_remove variable? input_domain (GroupID or AllBots), memory? input, array? remove Removes selected entities from input memory.
decorator_remove_key variable? input Removes input variable from script scope.
decorator_repeat Executes child functions in loop.
decorator_route_service array config (array routes, array strategies), vector? output_waypoint, string output_waypoint_name, string output_domain Unused.
decorator_run_once int max_attempts = 1 Executes child functions limited amount of times?
decorator_sensor flag entity_type_filter (ALL, PLAYERS, HUMAN_PLAYERS, NOISE, DAMAGE, AREA_DAMAGE, CLASSNAME, GRENADE), function? shape(flag type (sensor_shape_fov, sensor_shape_sphere), int radius), flag team_filter (ANY, CT, TERRORIST, SAME, OPPOSITE, ENEMY), int_flag orphan_only, int_flag priority, string class_name, vector? output Returns entity detected by sensor and executes child functions.
decorator_set_barrier Unused.
decorator_set_reaction_time array? input Executes child functions on input after delay, that depends of bot skill reaction time?
decorator_succeed Executes child functions if previous decorator is succeed?
decorator_tag_entity vector? input, array? output, flag operation_type (BT_DECORATOR_TAG_ENTITY_CLEAR, BT_DECORATOR_TAG_ENTITY_SET), int expiration_time ??? Used in picking target tree in Valve scripts.
decorator_tag_threshold vector? entity_input, vector? tagged_entities_input, int amount, flag check_type (BT_DECORATOR_TAG_THRESHOLD_AT_MOST, BT_DECORATOR_TAG_THRESHOLD_AT_LEAST) ??? Used to determine if it's safe to do objective in Valve scripts?
decorator_token_service variable? domain, string output_token_name, string output_token_domain, function config(array tokens, array assignments) In Guardian Mode: defines bot GroupID, then executes child functions.
decorator_try_lock variable? domain Checks if other bot is already doing same function???
decorator_wait_success int timeout Executres child functions after delay?
decorator_wait_success int timeout Executres child functions after delay?

Conditions

Type Parameters Description
condition_barrier Unused.
condition_distance_less vector input, int distance_threshold_min, int distance_threshold_max Returns true, if distance to input position is less than distance_threshold?
condition_has_parachute Returns true, if bot has parachute in inventory.
condition_inactive array input(memory? key), int round_start_threshold_seconds, int sensor_inactivity_threshold_seconds Returns true, if bot doesn't have any memory and sensor input within timing.
condition_is_airborne Returns true, if bot is mid-air.
condition_is_at_bomb_site Returns true, if bot is at bombsite zone.
condition_is_empty int_flag? global, any input Returns true, if input variable is empty or doesn't exist.
condition_is_equal any source, any destination Returns true, if source variable is equal to "destination" input.
condition_is_greater any source, any destination Unused. Returns true, if source variable is greater than "destination" input.
condition_is_greater_equal any source, any destination Unused. Returns true, if source variable is equal or greater than "destination" input.
condition_is_inv_slot_empty flag slot (KNIFE, PISTOL, RIFLE, GRENADES) Returns true, if input equipment slot is empty.
condition_is_less any source, any destination Unused. Returns true, if source variable is less than "destination" input.
condition_is_less_equal any source, any destination Unused. Returns true, if source variable is equal or less than "destination" input.
condition_is_reloading Unused. Returns true, if active weapon is in reloading state.
condition_is_weapon_equipped string weapon Returns true, if bot has active weapon with input classname.
condition_is_weapon_suitable string weapon Unused.
condition_out_of_ammo Returns true, if active weapon is out of ammo.
condition_owns_item string weapon Returns true, if bot has item with input classname.

Actions

Type Parameters Description
action_acquire_items array items, int_flag? remove_all_items Equips bot with items from array.
action_aim vector input, int_flag? acquire_only, flag? ready Rotates bot towards input point?
action_aim_projectile vector input, vector output Calculates angles for throwing at input position?
action_assign_guardian_loadout string input_token_name, array assignments(string token, array loadout(array items, array wave_numbers, int wave_numbers_min, int wave_numbers_max, int weight)) In Guardian mode: Chooses bot spawn loadout.
action_attack vector input, flag? output (e.g. output = "Attacking"), flag? ready (e.g. ready = "AimReady") Bot attack input entity?
action_buy Bot buys weapons.
action_choose_bomb_site_area int input, navzone? output Gets bombzone nav position from index. Supports convars.
action_choose_guardian_bomb_plant_location vector? output Chooses plant position in navmesh? Guardian mode only?
action_choose_random_waypoint navzone? input, vector output Chooses random waypoint inside input navzone.
action_choose_random_waypoint_within_radius vector origin, vector output, float radius Choose random waypoint within specified origin and radius.
action_choose_team_spawn_area navzone? output Gets all navzones with spawnpoints?
action_combat_positioning vector input, flag? is_attacking Bot tries to reach best combat position against input entity?
action_commit_suicide Kills bot.
action_compare_global_counter variable? input_name (e.g. input_name = "'Test'"), int input_value Compares value from variable "input_name" to input value.
action_coordinated_buy flag team_filter (ANY, CT, TERRORIST, SAME, OPPOSITE, ENEMY), int save_threshold, flag? id_no_purchase (e.g. id_no_purchase = "DidNotPurchase"), array purchases(array items, string id) In Guardian mode: restricts buying items to specific groupIDs?
action_crouch Forces bot to crouch.
action_custom_buy array item_aliases Unused.
action_drop_active_weapon Unused. Forces bot to drop active weapon.
action_equip_item string item, array items_one_of Forces bot to select item with classname from input.
action_equip_weapon string weapon (classname or BEST) Force bot to select item with classname from input or "best" weapon in inventory.
action_flee_area_damage vector? input, vector output, int max_search_range, int threat_min_keep_distance Returns safe spot from that position within search radius.
action_hide Unused.
action_inspect_current_weapon Unused. Forces bot to play inspect animation.
action_jump Forces bot to jump.
action_look_at vector input_angles, navzone? input_location Rotates bot at specified angle.
action_move_to vector destination, flag movement_type (BT_ACTION_MOVETO_RUN, BT_ACTION_MOVETO_WALK), flag route_type (BT_ACTION_MOVETO_FASTEST_ROUTE,BT_ACTION_MOVETO_SAFEST_ROUTE), vector? hiding_spot, vector? threat, int damaging_areas_penalty_cost, int nearest_area_distance_threshold, int hiding_spot_check_distance_threshold, int arrival_epsilon, float additional_arrival_epsilon_2d, int_flag? auto_look_adjust Forces bot to move at destination point.
action_parachute_positioning ???
action_pull_trigger int ratio Forces bot primary attack.
action_reload Forces bot to reload weapon.
action_say string phrase, flag? high_priority Forces bot to say radio command phrase. List of phrases is located in botchatter.db
action_secondary_attack Unused. Forces bot secondary attack.
action_select_areas_within_radius vector input, float radius, navzone? output Returns navzones within specified origin and radius?
action_set_global_counter variable? input_name, int input_value Sets input value to variable "input_name".
action_set_global_flag variable? name, int expiration_time_min, int expiration_time_max Sets global variable "name" to 1 for specified time?
action_set_value_float variable? key, float value Sets float value to variable "key".
action_set_value_vector variable? key, vector value Sets vector value to variable "key".
action_standup Unused. Forces bot to uncrouch.
action_teleport vector destination Teleports bot to destination position.
action_use Forces bot "+use"
action_wait int wait_time_min, int wait_time_max Freezes bot AI and script execution for defined amount of time.

Reserved Variables

Those variables are defined in game code. They can be used to get some information about game mode and bot and as conditions.

Variable Description
int NumberOfTerrorists Number of players in T team.
int NumberOfAliveTerrorists Number of alive players in T team.
int NumberOfCounterTerrorists Number of players in CT team.
int NumberOfAliveCounterTerrorists Number of alive players in CT team.
int GuardianWaveNumber Wave number in Guardian Mode.
int AccountBalance Amount of player money.
float? BlindnessPercentage Amount of blindness applied by flash grenade.
??? BombIsBeingDefused Returns ??? when bomb is being defused.
variable? LastCoopSpawnPointName Targetname of last spawn point spawned that bot in Co-op Strike.
Vector LastCoopSpawnPointLocation Origin point of last spawn point spawned that bot in Co-op Strike.
int AmmoCount/weapon_name Remained amount of ammo in weapon with classname "weapon_name" (clip + reserve).
int AmmoCount/current Remained amount of ammo in active weapon (clip + reserve).

Examples

Default Deathmatch Behavior Tree

Found in csgo/scripts/ai/bt_default.kv3.

 
<!-- kv3 encoding:text:version{e21c7f3c-8a33-41c5-9977-a76d3a32aa0d} format:generic:version{7412167c-06e9-4698-aff2-e63eb59037e7} -->
{
	config = "scripts/ai/deathmatch/bt_config.kv3"
	root =
	{
		type = "decorator_bot_service"
		memory_to_expire =
		[
			{
				key = "ShortTermAttackMemory"
				time = 0.7
				distance = 0
			},
			{
				key = "LongTermMemory"
				time = 10
				distance = 500
			},
			{
				key = "ShortTermInvestigateMemory"
				time = 3
				distance = 200
			}
		]
		child =
		{
			type = "decorator_buy_service"
			output = "ShouldBuy"
			child =
			{
				type = "parallel"
				children =
				[
					{
						type = "decorator_repeat"
						child =
						{
							type = "parallel"
							children =
							[
								// memorize enemies through vision
								{
									type = "subtree"
									file = "scripts/ai/modules/bt_memorize_enemies_vision.kv3"
									name = "MemorizeEnemiesVision"
								},
								// memorize noises happening right now
								{
									type = "subtree"
									file = "scripts/ai/modules/bt_memorize_noises.kv3"
									name = "MemorizeNoises"
								},
								// record the nearest memorized event to investigate
								{
									type = "subtree"
									file = "scripts/ai/modules/bt_memorize_nearest_investigation.kv3"
									name = "MemorizeNearestInvestigation"
								}
							]
						}
					},
					{
						type = "decorator_repeat"
						child =
						{
							type = "selector"
							children =
							[
								// Buy if we have to
								{
									type = "condition_is_empty"
									input = "ShouldBuy"
									negated = 1
									child =
									{
										// sequencer: evaluate first to last child, in order
										type = "sequencer"
										children =
										[
											{
												type = "action_wait"
												wait_time_min = 3
												wait_time_max = 3
											},
											{
												type = "action_buy"
											},
											{
												type = "decorator_remove_key"
												input = "ShouldBuy"
											}
										]
									}
								},
								// Else: face the damage source if we're taking damage
								{
									type = "decorator_sensor"
									entity_type_filter = "DAMAGE"
									output = "Damage"
									priority = 0
									child =
									{
										type = "condition_is_empty"
										input = "Damage"
										negated = 1
										child =
										{
											type = "action_aim"
											input = "Damage"
											acquire_only = 1
										}
									}
								},
								// Else: attack if we see an enemy
								{
									type = "subtree"
									file = "scripts/ai/modules/bt_attack.kv3"
									name = "Attack"
								},
								{
									type = "subtree"
									file = "scripts/ai/modules/bt_heal_if_needed.kv3"
									name = "HealIfNeeded"
								},
								// Else: investigate the closest memorized event
								{
									type = "subtree"
									file = "scripts/ai/modules/bt_investigate_closest_memorized_event.kv3"
									name = "InvestigateClosestMemorizedEvent"
								},
								// Else: hunt
								{
									// sequencer: evaluate first to last child, in order
									type = "sequencer"
									children =
									[
										{
											type = "action_equip_weapon"
											weapon = "BEST"
										},
										{
											type = "decorator_random_int"
											min = 0
											max = 1
											output = "BombSiteIndex"
											child =
											{
												type = "action_choose_bomb_site_area"
												input = "BombSiteIndex"
												output = "HuntAreas"
											}
										},
										{
											type = "action_choose_team_spawn_area"
											output = "HuntAreas"
										},
										{
											type = "action_choose_random_waypoint"
											input = "HuntAreas"
											output = "TargetHuntArea"
										},
										{
											type = "action_move_to"
											destination = "TargetHuntArea"
											movement_type = "BT_ACTION_MOVETO_RUN"
											route_type = "BT_ACTION_MOVETO_FASTEST_ROUTE"
										}
									]
								}
							]
						}
					}
				]
			}
		}
	}
}