Merge pull request #17 from GDQuest/features/special-agents

Introduce specialized smart agents

project/demos/Arrive/Arriver.gd

@@ -1,7 +1,7 @@
 extends KinematicBody2D
 
 
-var agent := GSTSteeringAgent.new()
+var agent := GSTKinematicBody2DAgent.new(self)
 var target := GSTAgentLocation.new()
 var arrive := GSTArrive.new(agent, target)
 var _accel := GSTTargetAcceleration.new()
@@ -11,11 +11,8 @@ var _drag := 0.1
 
 
 func _physics_process(delta: float) -> void:
-	_update_agent()
-	_accel = arrive.calculate_steering(_accel)
-	_velocity += Vector2(_accel.linear.x, _accel.linear.y)
-	_velocity = _velocity.linear_interpolate(Vector2.ZERO, _drag).clamped(agent.linear_speed_max)
-	_velocity = move_and_slide(_velocity)
+	arrive.calculate_steering(_accel)
+	agent._apply_steering(_accel, delta)
 
 
 func setup(
@@ -26,12 +23,7 @@ func setup(
 ) -> void:
 	agent.linear_speed_max = linear_speed_max
 	agent.linear_acceleration_max = linear_acceleration_max
-	agent.position = Vector3(global_position.x, global_position.y, 0)
+	agent.linear_drag_percentage = _drag
 	arrive.deceleration_radius = deceleration_radius
 	arrive.arrival_tolerance = arrival_tolerance
 	target.position = agent.position
-
-
-func _update_agent() -> void:
-	agent.position = Vector3(global_position.x, global_position.y, 0)
-	agent.linear_velocity = Vector3(_velocity.x, _velocity.y, 0)

project/demos/AvoidCollisions/Avoider.gd

@@ -13,7 +13,7 @@ var _drag := 0.1
 var _color := Color(0.4, 1.0, 0.89, 0.3)
 
 onready var collision := $CollisionShape2D
-onready var agent := GSTSteeringAgent.new()
+onready var agent := GSTKinematicBody2DAgent.new(self)
 onready var proximity := GSTRadiusProximity.new(agent, [], 140)
 onready var avoid := GSTAvoidCollisions.new(agent, proximity)
 onready var target := GSTAgentLocation.new()
@@ -27,12 +27,11 @@ func _draw() -> void:
 
 
 func _physics_process(delta: float) -> void:
-	_update_agent()
-	_accel = priority.calculate_steering(_accel)
-	_velocity += Vector2(_accel.linear.x, _accel.linear.y)
-	_velocity = _velocity.linear_interpolate(Vector2.ZERO, _drag)
-	_velocity = _velocity.clamped(agent.linear_speed_max)
-	_velocity = move_and_slide(_velocity)
+	target.position.x = agent.position.x + _direction.x*_radius
+	target.position.y = agent.position.y + _direction.y*_radius
+	
+	priority.calculate_steering(_accel)
+	agent._apply_steering(_accel, delta)
 
 
 func setup(
@@ -46,15 +45,19 @@ func setup(
 	) -> void:
 	rng.randomize()
 	_direction = Vector2(rng.randf_range(-1, 1), rng.randf_range(-1, 1)).normalized()
-	_update_agent()
+	
 	agent.linear_speed_max = linear_speed_max
 	agent.linear_acceleration_max = linear_accel_max
+	
 	proximity.radius = proximity_radius
 	_boundary_bottom = boundary_bottom
 	_boundary_right = boundary_right
+	
 	_radius = collision.shape.radius
 	agent.bounding_radius = _radius
 	
+	agent.linear_drag_percentage = _drag
+	
 	self.draw_proximity = draw_proximity
 	
 	priority.add(avoid)
@@ -84,12 +87,3 @@ func set_random_nonoverlapping_position(others: Array, distance_from_boundary_mi
 				done = false
 		if done:
 			break
-
-
-func _update_agent() -> void:
-	agent.position.x = global_position.x
-	agent.position.y = global_position.y
-	agent.linear_velocity.x = _velocity.x
-	agent.linear_velocity.y = _velocity.y
-	target.position.x = agent.position.x + _direction.x*_radius
-	target.position.y = agent.position.y + _direction.y*_radius

project/demos/Face/Turret.gd

@@ -2,7 +2,7 @@ extends KinematicBody2D
 
 
 var face: GSTFace
-var agent := GSTSteeringAgent.new()
+var agent := GSTKinematicBody2DAgent.new(self)
 
 var _accel := GSTTargetAcceleration.new()
 var _angular_drag := 0.1
@@ -19,15 +19,8 @@ func _ready() -> void:
 
 
 func _physics_process(delta: float) -> void:
-	_accel = face.calculate_steering(_accel)
-	agent.angular_velocity = clamp(
-			agent.angular_velocity + _accel.angular,
-			-agent.angular_speed_max,
-			agent.angular_speed_max
-	)
-	agent.angular_velocity = lerp(agent.angular_velocity, 0, _angular_drag)
-	agent.orientation += agent.angular_velocity * delta
-	rotation = agent.orientation
+	face.calculate_steering(_accel)
+	agent._apply_steering(_accel, delta)
 
 
 func _draw() -> void:
@@ -48,5 +41,4 @@ func setup(
 	
 	agent.angular_acceleration_max = angular_accel_max
 	agent.angular_speed_max = angular_speed_max
-	agent.position = Vector3(global_position.x, global_position.y, 0)
-
+	agent.angular_drag_percentage = _angular_drag

project/demos/FollowPath/PathFollower.gd

@@ -6,7 +6,7 @@ var _accel := GSTTargetAcceleration.new()
 var _valid := false
 var _drag := 0.1
 
-onready var agent := GSTSteeringAgent.new()
+onready var agent := GSTKinematicBody2DAgent.new(self)
 onready var path := GSTPath.new([
 		Vector3(global_position.x, global_position.y, 0),
 		Vector3(global_position.x, global_position.y, 0)
@@ -25,27 +25,18 @@ func setup(
 	owner.drawer.connect("path_established", self, "_on_Drawer_path_established")
 	follow.path_offset = path_offset
 	follow.prediction_time = predict_time
-	agent.linear_acceleration_max = accel_max
-	agent.linear_speed_max = speed_max
 	follow.deceleration_radius = decel_radius
 	follow.arrival_tolerance = arrival_tolerance
 	
+	agent.linear_acceleration_max = accel_max
+	agent.linear_speed_max = speed_max
+	agent.linear_drag_percentage = _drag
+
 
 func _physics_process(delta: float) -> void:
 	if _valid:
-		_update_agent()
-		_accel = follow.calculate_steering(_accel)
-		_velocity += Vector2(_accel.linear.x, _accel.linear.y)
-		_velocity = _velocity.linear_interpolate(Vector2.ZERO, _drag)
-		_velocity = _velocity.clamped(agent.linear_speed_max)
-		_velocity = move_and_slide(_velocity)
-
-
-func _update_agent() -> void:
-	agent.position.x = global_position.x
-	agent.position.y = global_position.y
-	agent.linear_velocity.x = _velocity.x
-	agent.linear_velocity.y = _velocity.y
+		follow.calculate_steering(_accel)
+		agent._apply_steering(_accel, delta)
 
 
 func _on_Drawer_path_established(points: Array) -> void:

project/demos/GroupBehaviors/Member.gd

@@ -4,7 +4,7 @@ extends KinematicBody2D
 var separation: GSTSeparation
 var cohesion: GSTCohesion
 var proximity: GSTRadiusProximity
-var agent := GSTSteeringAgent.new()
+var agent := GSTKinematicBody2DAgent.new(self)
 var blend := GSTBlend.new(agent)
 var acceleration := GSTTargetAcceleration.new()
 var draw_proximity := false
@@ -28,6 +28,7 @@ func setup(
 	
 	agent.linear_acceleration_max = linear_accel_max
 	agent.linear_speed_max = linear_speed_max
+	agent.linear_drag_percentage = 0.1
 	
 	proximity = GSTRadiusProximity.new(agent, [], proximity_radius)
 	separation = GSTSeparation.new(agent, proximity)
@@ -43,14 +44,9 @@ func _draw() -> void:
 
 
 func _physics_process(delta: float) -> void:
-	agent.position.x = global_position.x
-	agent.position.y = global_position.y
 	if blend:
-		acceleration = blend.calculate_steering(acceleration)
-		_velocity += Vector2(acceleration.linear.x, acceleration.linear.y)
-		_velocity = _velocity.linear_interpolate(Vector2.ZERO, 0.1)
-		_velocity = _velocity.clamped(agent.linear_speed_max)
-		move_and_slide(_velocity)
+		blend.calculate_steering(acceleration)
+		agent._apply_steering(acceleration, delta)
 
 
 func set_neighbors(neighbor: Array) -> void:

project/demos/PursueSeek/Pursuer.gd

@@ -4,71 +4,68 @@ extends KinematicBody2D
 
 export var use_seek: bool = false
 
-var _orient_behavior: GSTSteeringBehavior
-var _behavior: GSTSteeringBehavior
+var _blend: GSTBlend
 
-var _linear_velocity := Vector2()
 var _linear_drag_coefficient := 0.025
-var _angular_velocity := 0.0
 var _angular_drag := 0.1
 var _direction_face := GSTAgentLocation.new()
 
-onready var agent := GSTSteeringAgent.new()
+onready var agent := GSTKinematicBody2DAgent.new(self)
 onready var accel := GSTTargetAcceleration.new()
 onready var player_agent: GSTSteeringAgent = owner.find_node("Player", true, false).agent
 
 
 func _ready() -> void:
+	agent.calculate_velocities = false
 	set_physics_process(false)
 
 
 func _physics_process(delta: float) -> void:
-	_update_agent()
-	
-	accel = _behavior.calculate_steering(accel)
-	
 	_direction_face.position = agent.position + accel.linear.normalized()
 	
-	accel = _orient_behavior.calculate_steering(accel)
-	_angular_velocity += accel.angular
+	_blend.calculate_steering(accel)
 
-	_angular_velocity = clamp(
-			lerp(_angular_velocity, 0, _angular_drag),
+	agent.angular_velocity = clamp(
+			agent.angular_velocity + accel.angular,
 			-agent.angular_speed_max,
 			agent.angular_speed_max
 	)
+	agent.angular_velocity = lerp(agent.angular_velocity, 0, _angular_drag)
 
-	rotation += _angular_velocity * delta
+	rotation += agent.angular_velocity * delta
 	
-	_linear_velocity += GSTUtils.angle_to_vector2(rotation) * -agent.linear_acceleration_max
-	_linear_velocity = _linear_velocity.clamped(agent.linear_speed_max)
-	_linear_velocity = _linear_velocity.linear_interpolate(Vector2.ZERO, _linear_drag_coefficient)
-	_linear_velocity = move_and_slide(_linear_velocity)
+	var linear_velocity := (
+			GSTUtils.to_vector2(agent.linear_velocity) + 
+			(GSTUtils.angle_to_vector2(rotation) * -agent.linear_acceleration_max)
+	)
+	linear_velocity = linear_velocity.clamped(agent.linear_speed_max)
+	linear_velocity = linear_velocity.linear_interpolate(
+			Vector2.ZERO,
+			_linear_drag_coefficient
+	)
+	
+	linear_velocity = move_and_slide(linear_velocity)
+	agent.linear_velocity = GSTUtils.to_vector3(linear_velocity)
 
 
 func setup(predict_time: float, linear_speed_max: float, linear_accel_max: float) -> void:
+	var behavior: GSTSteeringBehavior
 	if use_seek:
-		_behavior = GSTSeek.new(agent, player_agent)
+		behavior = GSTSeek.new(agent, player_agent)
 	else:
-		_behavior = GSTPursue.new(agent, player_agent, predict_time)
+		behavior = GSTPursue.new(agent, player_agent, predict_time)
 	
-	_orient_behavior = GSTFace.new(agent, _direction_face)
-	_orient_behavior.alignment_tolerance = deg2rad(5)
-	_orient_behavior.deceleration_radius = deg2rad(5)
+	var orient_behavior := GSTFace.new(agent, _direction_face)
+	orient_behavior.alignment_tolerance = deg2rad(5)
+	orient_behavior.deceleration_radius = deg2rad(5)
+	
+	_blend = GSTBlend.new(agent)
+	_blend.add(behavior, 1)
+	_blend.add(orient_behavior, 1)
 	
 	agent.angular_acceleration_max = deg2rad(40)
 	agent.angular_speed_max = deg2rad(90)
 	agent.linear_acceleration_max = linear_accel_max
 	agent.linear_speed_max = linear_speed_max
 	
-	_update_agent()
 	set_physics_process(true)
-
-
-func _update_agent() -> void:
-	agent.position.x = global_position.x
-	agent.position.y = global_position.y
-	agent.orientation = rotation
-	agent.linear_velocity.x = _linear_velocity.x
-	agent.linear_velocity.y = _linear_velocity.y
-	agent.angular_velocity = _angular_velocity

project/demos/SeekFlee/Seeker.gd

@@ -1,5 +1,4 @@
 extends KinematicBody2D
-# AI agent that uses the Seek behavior to hone in on the player's location as directly as possible.
 
 
 var player_agent: GSTAgentLocation
@@ -8,7 +7,7 @@ var start_speed: float
 var start_accel: float
 var use_seek := true
 
-onready var agent := GSTSteeringAgent.new()
+onready var agent := GSTKinematicBody2DAgent.new(self)
 onready var accel := GSTTargetAcceleration.new()
 onready var seek := GSTSeek.new(agent, player_agent)
 onready var flee := GSTFlee.new(agent, player_agent)
@@ -23,18 +22,9 @@ func _physics_process(delta: float) -> void:
 	if not player_agent:
 		return
 	
-	_update_agent()
 	if use_seek:
-		accel = seek.calculate_steering(accel)
+		seek.calculate_steering(accel)
 	else:
-		accel = flee.calculate_steering(accel)
+		flee.calculate_steering(accel)
 	
-	velocity = (velocity + Vector2(accel.linear.x, accel.linear.y)).clamped(agent.linear_speed_max)
-	velocity = move_and_slide(velocity)
-
-
-func _update_agent() -> void:
-	agent.position.x = global_position.x
-	agent.position.y = global_position.y
-	agent.linear_velocity.x = velocity.x
-	agent.linear_velocity.y = velocity.y
+	agent._apply_steering(accel, delta)

project/project.godot

@@ -64,6 +64,16 @@ _global_script_classes=[ {
 "language": "GDScript",
 "path": "res://src/Proximities/GSTInfiniteProximity.gd"
 }, {
+"base": "GSTSpecializedAgent",
+"class": "GSTKinematicBody2DAgent",
+"language": "GDScript",
+"path": "res://src/Agents/GSTKinematicBody2DAgent.gd"
+}, {
+"base": "GSTSpecializedAgent",
+"class": "GSTKinematicBodyAgent",
+"language": "GDScript",
+"path": "res://src/Agents/GSTKinematicBodyAgent.gd"
+}, {
 "base": "GSTMatchOrientation",
 "class": "GSTLookWhereYouGo",
 "language": "GDScript",
@@ -99,6 +109,16 @@ _global_script_classes=[ {
 "language": "GDScript",
 "path": "res://src/Proximities/GSTRadiusProximity.gd"
 }, {
+"base": "GSTSpecializedAgent",
+"class": "GSTRigidBody2DAgent",
+"language": "GDScript",
+"path": "res://src/Agents/GSTRigidBody2DAgent.gd"
+}, {
+"base": "GSTSpecializedAgent",
+"class": "GSTRigidBodyAgent",
+"language": "GDScript",
+"path": "res://src/Agents/GSTRigidBodyAgent.gd"
+}, {
 "base": "GSTSteeringBehavior",
 "class": "GSTSeek",
 "language": "GDScript",
@@ -109,6 +129,11 @@ _global_script_classes=[ {
 "language": "GDScript",
 "path": "res://src/Behaviors/GSTSeparation.gd"
 }, {
+"base": "GSTSteeringAgent",
+"class": "GSTSpecializedAgent",
+"language": "GDScript",
+"path": "res://src/Agents/GSTSpecializedAgent.gd"
+}, {
 "base": "GSTAgentLocation",
 "class": "GSTSteeringAgent",
 "language": "GDScript",
@@ -128,6 +153,11 @@ _global_script_classes=[ {
 "class": "GSTUtils",
 "language": "GDScript",
 "path": "res://src/GSTUtils.gd"
+}, {
+"base": "EditorScript",
+"class": "ReferenceCollector",
+"language": "GDScript",
+"path": "res://ReferenceCollector.gd"
 } ]
 _global_script_class_icons={
 "GSTAgentLocation": "",
@@ -141,6 +171,8 @@ _global_script_class_icons={
 "GSTFollowPath": "",
 "GSTGroupBehavior": "",
 "GSTInfiniteProximity": "",
+"GSTKinematicBody2DAgent": "",
+"GSTKinematicBodyAgent": "",
 "GSTLookWhereYouGo": "",
 "GSTMatchOrientation": "",
 "GSTPath": "",
@@ -148,12 +180,16 @@ _global_script_class_icons={
 "GSTProximity": "",
 "GSTPursue": "",
 "GSTRadiusProximity": "",
+"GSTRigidBody2DAgent": "",
+"GSTRigidBodyAgent": "",
 "GSTSeek": "",
 "GSTSeparation": "",
+"GSTSpecializedAgent": "",
 "GSTSteeringAgent": "",
 "GSTSteeringBehavior": "",
 "GSTTargetAcceleration": "",
-"GSTUtils": ""
+"GSTUtils": "",
+"ReferenceCollector": ""
 }
 
 [application]

project/src/Agents/GSTKinematicBody2DAgent.gd

@@ -0,0 +1,134 @@
+# A specialized steering agent that updates itself every frame so the user does
+# not have to using a KinematicBody2D
+extends GSTSpecializedAgent
+class_name GSTKinematicBody2DAgent
+
+
+# SLIDE uses `move_and_slide`
+# COLLIDE uses `move_and_collide`
+# POSITION changes the `global_position` directly
+enum MovementType { SLIDE, COLLIDE, POSITION }
+
+
+# The KinematicBody2D to keep track of
+var body: KinematicBody2D setget _set_body
+
+# The type of movement the body executes
+var movement_type: int
+
+var _last_position: Vector2
+
+
+func _init(body: KinematicBody2D, movement_type: int = MovementType.SLIDE) -> void:
+	if not body.is_inside_tree():
+		yield(body, "ready")
+	
+	self.body = body
+	self.movement_type = movement_type
+	
+	body.get_tree().connect("physics_frame", self, "_on_SceneTree_physics_frame")
+
+
+# Moves the agent's `body` by target `acceleration`.
+# tags: virtual
+func _apply_steering(acceleration: GSTTargetAcceleration, delta: float) -> void:
+	_applied_steering = true
+	match movement_type:
+		MovementType.COLLIDE:
+			_apply_collide_steering(acceleration.linear, delta)
+		MovementType.SLIDE:
+			_apply_sliding_steering(acceleration.linear)
+		_:
+			_apply_position_steering(acceleration.linear, delta)
+	
+	_apply_orientation_steering(acceleration.angular, delta)
+
+
+func _apply_sliding_steering(accel: Vector3) -> void:
+	var velocity := GSTUtils.to_vector2(linear_velocity + accel).clamped(linear_speed_max)
+	if apply_linear_drag:
+		velocity = velocity.linear_interpolate(Vector2.ZERO, linear_drag_percentage)
+	velocity = body.move_and_slide(velocity)
+	if calculate_velocities:
+		linear_velocity = GSTUtils.to_vector3(velocity)
+
+
+func _apply_collide_steering(accel: Vector3, delta: float) -> void:
+	var velocity := GSTUtils.clampedv3(linear_velocity + accel, linear_speed_max)
+	if apply_linear_drag:
+		velocity = velocity.linear_interpolate(
+				Vector3.ZERO,
+				linear_drag_percentage
+		)
+	body.move_and_collide(GSTUtils.to_vector2(velocity) * delta)
+	if calculate_velocities:
+		linear_velocity = velocity
+
+
+func _apply_position_steering(accel: Vector3, delta: float) -> void:
+	var velocity := GSTUtils.clampedv3(linear_velocity + accel, linear_speed_max)
+	if apply_linear_drag:
+		velocity = velocity.linear_interpolate(
+				Vector3.ZERO,
+				linear_drag_percentage
+		)
+	body.global_position += GSTUtils.to_vector2(velocity) * delta
+	if calculate_velocities:
+		linear_velocity = velocity
+
+
+func _apply_orientation_steering(angular_acceleration: float, delta: float) -> void:
+	var velocity = angular_velocity + angular_acceleration
+	if apply_angular_drag:
+		velocity = lerp(velocity, 0, angular_drag_percentage)
+	body.rotation += velocity * delta
+	if calculate_velocities:
+		angular_velocity = velocity
+
+
+func _set_body(value: KinematicBody2D) -> void:
+	body = value
+	
+	_last_position = body.global_position
+	_last_orientation = body.rotation
+	
+	position = GSTUtils.to_vector3(_last_position)
+	orientation = _last_orientation
+
+
+func _on_SceneTree_physics_frame() -> void:
+	var current_position: Vector2 = body.global_position
+	var current_orientation: float = body.rotation
+	
+	position = GSTUtils.to_vector3(current_position)
+	orientation = current_orientation
+	
+	if calculate_velocities:
+		if _applied_steering:
+			_applied_steering = false
+		else:
+			linear_velocity = GSTUtils.clampedv3(
+				GSTUtils.to_vector3(_last_position - current_position),
+				linear_speed_max
+			)
+			if apply_linear_drag:
+				linear_velocity = linear_velocity.linear_interpolate(
+					Vector3.ZERO,
+					linear_drag_percentage
+				)
+			
+			angular_velocity = clamp(
+				_last_orientation - current_orientation,
+				-angular_speed_max,
+				angular_speed_max
+			)
+			
+			if apply_angular_drag:
+				angular_velocity = lerp(
+					angular_velocity,
+					0,
+					angular_drag_percentage
+			)
+			
+			_last_position = current_position
+			_last_orientation = current_orientation

project/src/Agents/GSTKinematicBodyAgent.gd

@@ -0,0 +1,133 @@
+# A specialized steering agent that updates itself every frame so the user does
+# not have to using a KinematicBody
+extends GSTSpecializedAgent
+class_name GSTKinematicBodyAgent
+
+# SLIDE uses `move_and_slide`
+# COLLIDE uses `move_and_collide`
+# POSITION changes the global_position directly
+enum MovementType { SLIDE, COLLIDE, POSITION }
+
+
+# The KinematicBody to keep track of
+var body: KinematicBody setget _set_body
+
+# The type of movement the body executes
+var movement_type: int
+
+var _last_position: Vector3
+
+
+func _init(body: KinematicBody, movement_type: int = MovementType.SLIDE) -> void:
+	if not body.is_inside_tree():
+		yield(body, "ready")
+	
+	self.body = body
+	self.movement_type = movement_type
+	
+	body.get_tree().connect("physics_frame", self, "_on_SceneTree_physics_frame")
+
+
+# Moves the agent's `body` by target `acceleration`.
+# tags: virtual
+func _apply_steering(acceleration: GSTTargetAcceleration, delta: float) -> void:
+	_applied_steering = true
+	match movement_type:
+		MovementType.COLLIDE:
+			_apply_collide_steering(acceleration.linear, delta)
+		MovementType.SLIDE:
+			_apply_sliding_steering(acceleration.linear)
+		_:
+			_apply_position_steering(acceleration.linear, delta)
+	
+	_apply_orientation_steering(acceleration.angular, delta)
+
+
+func _apply_sliding_steering(accel: Vector3) -> void:
+	var velocity := GSTUtils.clampedv3(linear_velocity + accel, linear_speed_max)
+	if apply_linear_drag:
+		velocity = velocity.linear_interpolate(Vector3.ZERO, linear_drag_percentage)
+	velocity = body.move_and_slide(velocity)
+	if calculate_velocities:
+		linear_velocity = velocity
+
+
+func _apply_collide_steering(accel: Vector3, delta: float) -> void:
+	var velocity := GSTUtils.clampedv3(linear_velocity + accel, linear_speed_max)
+	if apply_linear_drag:
+		velocity = velocity.linear_interpolate(
+				Vector3.ZERO,
+				linear_drag_percentage
+		)
+	body.move_and_collide(velocity * delta)
+	if calculate_velocities:
+		linear_velocity = velocity
+
+
+func _apply_position_steering(accel: Vector3, delta: float) -> void:
+	var velocity := GSTUtils.clampedv3(linear_velocity + accel, linear_speed_max)
+	if apply_linear_drag:
+		velocity = velocity.linear_interpolate(
+				Vector3.ZERO,
+				linear_drag_percentage
+		)
+	body.global_position += velocity * delta
+	if calculate_velocities:
+		linear_velocity = velocity
+
+
+func _apply_orientation_steering(angular_acceleration: float, delta: float) -> void:
+	var velocity = angular_velocity + angular_acceleration
+	if apply_angular_drag:
+		velocity = lerp(velocity, 0, angular_drag_percentage)
+	body.rotation.y += velocity * delta
+	if calculate_velocities:
+		angular_velocity = velocity
+
+
+func _set_body(value: KinematicBody) -> void:
+	body = value
+	
+	_last_position = body.global_position
+	_last_orientation = body.rotation.y
+	
+	position = _last_position
+	orientation = _last_orientation
+
+
+func _on_SceneTree_physics_frame() -> void:
+	var current_position: Vector3 = body.global_position
+	var current_orientation: float = body.rotation.y
+	
+	position = current_position
+	orientation = current_orientation
+	
+	if calculate_velocities:
+		if _applied_steering:
+			_applied_steering = false
+		else:
+			linear_velocity = GSTUtils.clampedv3(
+				_last_position - current_position,
+				linear_speed_max
+			)
+			if apply_linear_drag:
+				linear_velocity = linear_velocity.linear_interpolate(
+					Vector3.ZERO,
+					linear_drag_percentage
+				)
+			
+			angular_velocity = clamp(
+				_last_orientation - current_orientation,
+				-angular_speed_max,
+				angular_speed_max
+			)
+			
+			if apply_angular_drag:
+				angular_velocity = lerp(
+					angular_velocity,
+					0,
+					angular_drag_percentage
+			)
+			
+			_last_position = current_position
+			_last_orientation = current_orientation

project/src/Agents/GSTRigidBody2DAgent.gd

@@ -0,0 +1,58 @@
+# A specialized steering agent that updates itself every frame so the user does
+# not have to using a RigidBody2D
+extends GSTSpecializedAgent
+class_name GSTRigidBody2DAgent
+
+
+# The RigidBody2D to keep track of
+var body: RigidBody2D setget _set_body
+
+var _last_position: Vector2
+
+
+func _init(body: RigidBody2D) -> void:
+	if not body.is_inside_tree():
+		yield(body, "ready")
+	
+	self.body = body
+
+
+# Moves the agent's `body` by target `acceleration`.
+# tags: virtual
+func _apply_steering(acceleration: GSTTargetAcceleration, delta: float) -> void:
+	_applied_steering = true
+	body.apply_central_impulse(GSTUtils.to_vector2(acceleration.linear))
+	body.apply_torque_impulse(acceleration.angular)
+	if calculate_velocities:
+		linear_velocity = GSTUtils.to_vector3(body.linear_velocity)
+		angular_velocity = body.angular_velocity
+
+
+func _set_body(value: RigidBody2D) -> void:
+	body = value
+	
+	_last_position = body.global_position
+	_last_orientation = body.rotation
+	
+	position = GSTUtils.to_vector3(_last_position)
+	orientation = _last_orientation
+
+
+func _on_body_ready() -> void:
+	body.get_tree().connect("physics_frame", self, "_on_SceneTree_frame")
+	_set_body(body)
+
+
+func _on_SceneTree_frame() -> void:
+	var current_position: Vector2 = body.global_position
+	var current_orientation: float = body.rotation
+	
+	position = GSTUtils.to_vector3(current_position)
+	orientation = current_orientation
+	
+	if calculate_velocities:
+		if _applied_steering:
+			_applied_steering = false
+		else:
+			linear_velocity = GSTUtils.to_vector3(body.linear_velocity)
+			angular_velocity = body.angular_velocity

project/src/Agents/GSTRigidBodyAgent.gd

@@ -0,0 +1,60 @@
+# A specialized steering agent that updates itself every frame so the user does
+# not have to using a RigidBody
+extends GSTSpecializedAgent
+class_name GSTRigidBodyAgent
+
+
+# The RigidBody to keep track of
+var body: RigidBody setget _set_body
+
+var _last_position: Vector3
+
+
+func _init(body: RigidBody) -> void:
+	if not body.is_inside_tree():
+		yield(body, "ready")
+	
+	self.body = body
+	body.get_tree().connect("physics_frame", self, "_on_SceneTree_frame")
+	
+
+
+# Moves the agent's `body` by target `acceleration`.
+# tags: virtual
+func _apply_steering(acceleration: GSTTargetAcceleration, delta: float) -> void:
+	_applied_steering = true
+	body.apply_central_impulse(acceleration.linear)
+	body.apply_torque_impulse(Vector3.UP * acceleration.angular)
+	if calculate_velocities:
+		linear_velocity = body.linear_velocity
+		angular_velocity = body.angular_velocity.y
+
+
+func _set_body(value: RigidBody) -> void:
+	body = value
+	
+	_last_position = body.global_position
+	_last_orientation = body.rotation.y
+	
+	position = _last_position
+	orientation = _last_orientation
+
+
+func _on_body_ready() -> void:
+	body.get_tree().connect("physics_frame", self, "_on_SceneTree_frame")
+	_set_body(body)
+
+
+func _on_SceneTree_frame() -> void:
+	var current_position: Vector3 = body.global_position
+	var current_orientation: float = body.rotation.y
+	
+	position = current_position
+	orientation = current_orientation
+	
+	if calculate_velocities:
+		if _applied_steering:
+			_applied_steering = false
+		else:
+			linear_velocity = body.linear_velocity
+			angular_velocity = body.angular_velocity.y

project/src/Agents/GSTSpecializedAgent.gd

@@ -0,0 +1,40 @@
+# A base class for a specialized steering agent that updates itself every frame
+# so the user does not have to. All other specialized agents derive from this.
+# tags: abstract
+extends GSTSteeringAgent
+class_name GSTSpecializedAgent
+
+
+# If `true`, calculates linear and angular velocities based on the previous
+# frame. When `false`, the user must keep those values updated.
+var calculate_velocities := true
+
+# If `true` and `calculate_velocities` is true, interpolates
+# the current linear velocity towards 0 by the `linear_drag_percentage` value.
+# Does not apply to `RigidBody` and `RigidBody2D` nodes.
+var apply_linear_drag := true
+
+# If `true` and `calculate_velocities` is true, interpolates
+# the current angular velocity towards 0 by the `angular_drag_percentage` value.
+# Does not apply to `RigidBody` and `RigidBody2D` nodes.
+var apply_angular_drag := true
+
+# The percentage between the current linear velocity and 0 to interpolate by if
+# `calculate_velocities` and `apply_linear_drag` are true.
+# Does not apply to `RigidBody` and `RigidBody2D` nodes.
+var linear_drag_percentage := 0.0
+
+# The percentage between the current angular velocity and 0 to interpolate by if
+# `calculate_velocities` and `apply_angular_drag` are true.
+# Does not apply to `RigidBody` and `RigidBody2D` nodes.
+var angular_drag_percentage := 0.0
+
+var _last_orientation: float
+var _body_type: int
+var _applied_steering := false
+
+
+# Moves the agent's body by target `acceleration`.
+# tags: virtual
+func _apply_steering(acceleration: GSTTargetAcceleration, delta: float) -> void:
+	pass

project/src/Behaviors/GSTArrive.gd

@@ -19,7 +19,7 @@ func _init(agent: GSTSteeringAgent, target: GSTAgentLocation).(agent) -> void:
 	self.target = target
 
 
-func _arrive(acceleration: GSTTargetAcceleration, target_position: Vector3) -> GSTTargetAcceleration:
+func _arrive(acceleration: GSTTargetAcceleration, target_position: Vector3) -> void:
 	var to_target := target_position - agent.position
 	var distance := to_target.length()
 
@@ -38,8 +38,6 @@ func _arrive(acceleration: GSTTargetAcceleration, target_position: Vector3) -> G
 		acceleration.linear = GSTUtils.clampedv3(desired_velocity, agent.linear_acceleration_max)
 		acceleration.angular = 0
 
-	return acceleration
 
-
-func _calculate_steering(acceleration: GSTTargetAcceleration) -> GSTTargetAcceleration:
-	return _arrive(acceleration, target.position)
+func _calculate_steering(acceleration: GSTTargetAcceleration) -> void:
+	_arrive(acceleration, target.position)

project/src/Behaviors/GSTAvoidCollisions.gd

@@ -16,7 +16,7 @@ func _init(agent: GSTSteeringAgent, proximity: GSTProximity).(agent, proximity)
 	pass
 
 
-func _calculate_steering(acceleration: GSTTargetAcceleration) -> GSTTargetAcceleration:
+func _calculate_steering(acceleration: GSTTargetAcceleration) -> void:
 	_shortest_time = INF
 	_first_neighbor = null
 	_first_minimum_separation = 0
@@ -37,8 +37,6 @@ func _calculate_steering(acceleration: GSTTargetAcceleration) -> GSTTargetAccele
 	acceleration.linear = acceleration.linear.normalized() * -agent.linear_acceleration_max
 	acceleration.angular = 0
 
-	return acceleration
-
 
 # Callback for the proximity to call when finding neighbors. Keeps track of every `neighbor`
 # that was found but only keeps the one the owning agent will most likely collide with.

project/src/Behaviors/GSTBlend.gd

@@ -33,7 +33,7 @@ func get_behavior_at(index: int) -> Dictionary:
 	return {}
 
 
-func _calculate_steering(blended_accel: GSTTargetAcceleration) -> GSTTargetAcceleration:
+func _calculate_steering(blended_accel: GSTTargetAcceleration) -> void:
 	blended_accel.set_zero()
 
 	for i in range(_behaviors.size()):
@@ -48,5 +48,3 @@ func _calculate_steering(blended_accel: GSTTargetAcceleration) -> GSTTargetAccel
 			-agent.angular_acceleration_max,
 			agent.angular_acceleration_max
 	)
-
-	return blended_accel

project/src/Behaviors/GSTCohesion.gd

@@ -11,14 +11,13 @@ func _init(agent: GSTSteeringAgent, proximity: GSTProximity).(agent, proximity)
 	pass
 
 
-func _calculate_steering(acceleration: GSTTargetAcceleration) -> GSTTargetAcceleration:
+func _calculate_steering(acceleration: GSTTargetAcceleration) -> void:
 	acceleration.set_zero()
 	_center_of_mass = Vector3.ZERO
 	var neighbor_count = proximity._find_neighbors(_callback)
 	if neighbor_count > 0:
 		_center_of_mass *= 1.0 / neighbor_count
 		acceleration.linear = (_center_of_mass - agent.position).normalized() * agent.linear_acceleration_max
-	return acceleration
 
 
 # Callback for the proximity to call when finding neighbors. Adds `neighbor`'s position

project/src/Behaviors/GSTFace.gd

@@ -8,17 +8,16 @@ func _init(agent: GSTSteeringAgent, target: GSTAgentLocation).(agent, target) ->
 	pass
 
 
-func _face(acceleration: GSTTargetAcceleration, target_position: Vector3) -> GSTTargetAcceleration:
+func _face(acceleration: GSTTargetAcceleration, target_position: Vector3) -> void:
 	var to_target := target_position - agent.position
 	var distance_squared := to_target.length_squared()
 
 	if distance_squared < agent.zero_linear_speed_threshold:
 		acceleration.set_zero()
-		return acceleration
 	else:
 		var orientation = GSTUtils.vector3_to_angle(to_target)
-		return _match_orientation(acceleration, orientation)
+		_match_orientation(acceleration, orientation)
 
 
-func _calculate_steering(acceleration: GSTTargetAcceleration) -> GSTTargetAcceleration:
-	return _face(acceleration, target.position)
+func _calculate_steering(acceleration: GSTTargetAcceleration) -> void:
+	_face(acceleration, target.position)

project/src/Behaviors/GSTFlee.gd

@@ -7,9 +7,7 @@ func _init(agent: GSTSteeringAgent, target: GSTAgentLocation).(agent, target) ->
 	pass
 
 
-func _calculate_steering(acceleration: GSTTargetAcceleration) -> GSTTargetAcceleration:
+func _calculate_steering(acceleration: GSTTargetAcceleration) -> void:
 	acceleration.linear = (
 			(agent.position - target.position).normalized() * agent.linear_acceleration_max)
 	acceleration.angular = 0
-
-	return acceleration

project/src/Behaviors/GSTFollowPath.gd

@@ -25,7 +25,7 @@ func _init(
 	self.prediction_time = prediction_time
 
 
-func _calculate_steering(acceleration: GSTTargetAcceleration) -> GSTTargetAcceleration:
+func _calculate_steering(acceleration: GSTTargetAcceleration) -> void:
 	var location := (
 			agent.position if prediction_time == 0
 			else agent.position + (agent.linear_velocity * prediction_time))
@@ -38,13 +38,13 @@ func _calculate_steering(acceleration: GSTTargetAcceleration) -> GSTTargetAccele
 	if is_arrive_enabled and path.is_open:
 		if path_offset >= 0:
 			if target_distance > path.length - deceleration_radius:
-				return _arrive(acceleration, target_position)
+				_arrive(acceleration, target_position)
+				return
 		else:
 			if target_distance < deceleration_radius:
-				return _arrive(acceleration, target_position)
+				_arrive(acceleration, target_position)
+				return
 
 	acceleration.linear = (target_position - agent.position).normalized()
 	acceleration.linear *= agent.linear_acceleration_max
 	acceleration.angular = 0
-
-	return acceleration

project/src/Behaviors/GSTLookWhereYouGo.gd

@@ -8,10 +8,9 @@ func _init(agent: GSTSteeringAgent).(agent, null) -> void:
 	pass
 
 
-func _calculate_steering(accel: GSTTargetAcceleration) -> GSTTargetAcceleration:
+func _calculate_steering(accel: GSTTargetAcceleration) -> void:
 	if agent.linear_velocity.length_squared() < agent.zero_linear_speed_threshold:
 		accel.set_zero()
-		return accel
 	else:
 		var orientation := GSTUtils.vector3_to_angle(agent.linear_velocity)
-		return _match_orientation(accel, orientation)
+		_match_orientation(accel, orientation)

project/src/Behaviors/GSTMatchOrientation.gd

@@ -20,7 +20,7 @@ func _init(agent: GSTSteeringAgent, target: GSTAgentLocation).(agent) -> void:
 	self.target = target
 
 
-func _match_orientation(acceleration: GSTTargetAcceleration, desired_orientation: float) -> GSTTargetAcceleration:
+func _match_orientation(acceleration: GSTTargetAcceleration, desired_orientation: float) -> void:
 	var rotation := wrapf(desired_orientation - agent.orientation, -PI, PI)
 
 	var rotation_size := abs(rotation)
@@ -43,8 +43,6 @@ func _match_orientation(acceleration: GSTTargetAcceleration, desired_orientation
 
 	acceleration.linear = Vector3.ZERO
 
-	return acceleration
 
-
-func _calculate_steering(acceleration: GSTTargetAcceleration) -> GSTTargetAcceleration:
-	return _match_orientation(acceleration, target.orientation)
+func _calculate_steering(acceleration: GSTTargetAcceleration) -> void:
+	_match_orientation(acceleration, target.orientation)

project/src/Behaviors/GSTPriority.gd

@@ -31,7 +31,7 @@ func get_behavior_at(index: int) -> GSTSteeringBehavior:
 	return null
 
 
-func _calculate_steering(accel: GSTTargetAcceleration) -> GSTTargetAcceleration:
+func _calculate_steering(accel: GSTTargetAcceleration) -> void:
 	var threshold_squared := zero_threshold * zero_threshold
 
 	last_selected_index = -1
@@ -48,5 +48,3 @@ func _calculate_steering(accel: GSTTargetAcceleration) -> GSTTargetAcceleration:
 				break
 	else:
 		accel.set_zero()
-
-	return accel

project/src/Behaviors/GSTPursue.gd

@@ -19,7 +19,7 @@ func _init(
 	self.predict_time_max = predict_time_max
 
 
-func _calculate_steering(acceleration: GSTTargetAcceleration) -> GSTTargetAcceleration:
+func _calculate_steering(acceleration: GSTTargetAcceleration) -> void:
 	var target_position := target.position
 	var distance_squared := (target_position - agent.position).length_squared()
 
@@ -37,8 +37,6 @@ func _calculate_steering(acceleration: GSTTargetAcceleration) -> GSTTargetAccele
 
 	acceleration.angular = 0
 
-	return acceleration
-
 
 func _get_modified_acceleration() -> float:
 	return agent.linear_acceleration_max

project/src/Behaviors/GSTSeek.gd

@@ -12,9 +12,7 @@ func _init(agent: GSTSteeringAgent, target: GSTAgentLocation).(agent) -> void:
 	self.target = target
 
 
-func _calculate_steering(acceleration: GSTTargetAcceleration) -> GSTTargetAcceleration:
+func _calculate_steering(acceleration: GSTTargetAcceleration) -> void:
 	acceleration.linear = (
 			(target.position - agent.position).normalized() * agent.linear_acceleration_max)
 	acceleration.angular = 0
-
-	return acceleration

project/src/Behaviors/GSTSeparation.gd

@@ -18,11 +18,10 @@ func _init(agent: GSTSteeringAgent, proximity: GSTProximity).(agent, proximity)
 	pass
 
 
-func _calculate_steering(acceleration: GSTTargetAcceleration) -> GSTTargetAcceleration:
+func _calculate_steering(acceleration: GSTTargetAcceleration) -> void:
 	acceleration.set_zero()
 	self._acceleration = acceleration
 	proximity._find_neighbors(_callback)
-	return acceleration
 
 
 # Callback for the proximity to call when finding neighbors. Determines the amount of

project/src/GSTSteeringBehavior.gd

@@ -18,16 +18,13 @@ func _init(agent: GSTSteeringAgent) -> void:
 	self.agent = agent
 
 
-# Returns the `acceleration` modified with the behavior's desired amount of
-# acceleration.
-func calculate_steering(acceleration: GSTTargetAcceleration) -> GSTTargetAcceleration:
+# Sets the `acceleration` with the behavior's desired amount of acceleration.
+func calculate_steering(acceleration: GSTTargetAcceleration) -> void:
 	if is_enabled:
-		return _calculate_steering(acceleration)
+		_calculate_steering(acceleration)
 	else:
 		acceleration.set_zero()
-		return acceleration
 
 
-func _calculate_steering(acceleration: GSTTargetAcceleration) -> GSTTargetAcceleration:
+func _calculate_steering(acceleration: GSTTargetAcceleration) -> void:
 	acceleration.set_zero()
-	return acceleration

project/src/GSTUtils.gd

@@ -25,3 +25,13 @@ static func vector3_to_angle(vector: Vector3) -> float:
 # rotate around the Y axis.
 static func angle_to_vector2(angle: float) -> Vector2:
 	return Vector2(sin(-angle), cos(angle))
+
+
+# Returns a vector2 with `vector`'s x and y components.
+static func to_vector2(vector: Vector3) -> Vector2:
+	return Vector2(vector.x, vector.y)
+
+
+# Returns a vector3 with `vector`'s x and y components and 0 in z.
+static func to_vector3(vector: Vector2) -> Vector3:
+	return Vector3(vector.x, vector.y, 0)