Counter-Strike: Global Offensive/Bot Behavior Trees

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In Template:Game name, 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 Co-op Strike, Guardian and 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} -->

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"
										}
									]
								}
							]
						}
					}
				]
			}
		}
	}
}