From fa804f3f6db8fc2d20ab46d7ea4a3fbda092cfe6 Mon Sep 17 00:00:00 2001
From: Serhii Snitsaruk <limbonaut@pm.me>
Date: Thu, 1 Feb 2024 19:33:22 +0100
Subject: [PATCH] Demo: Implement basic knockback

---
 demo/demo/agents/agent_base.tscn             | 46 +++++++++++++++++---
 demo/demo/agents/player/player.tscn          |  5 +++
 demo/demo/agents/player/states/move_state.gd |  4 +-
 demo/demo/agents/scripts/agent_base.gd       | 20 ++++++---
 demo/demo/agents/scripts/health.gd           |  6 +--
 demo/demo/agents/scripts/hitbox.gd           | 18 +++++---
 demo/demo/agents/scripts/hurtbox.gd          |  7 +--
 demo/demo/ai/tasks/arrive_pos.gd             |  4 +-
 demo/demo/ai/tasks/leap_forward.gd           |  4 +-
 demo/demo/ai/tasks/pursue.gd                 |  4 +-
 10 files changed, 90 insertions(+), 28 deletions(-)

diff --git a/demo/demo/agents/agent_base.tscn b/demo/demo/agents/agent_base.tscn
index 70681a1..e8aa20e 100644
--- a/demo/demo/agents/agent_base.tscn
+++ b/demo/demo/agents/agent_base.tscn
@@ -38,10 +38,10 @@ scale_max = 1.2
 scale_curve = SubResource("CurveTexture_sb0wp")
 
 [sub_resource type="RectangleShape2D" id="RectangleShape2D_2k81i"]
-size = Vector2(100, 35)
+size = Vector2(130, 35)
 
 [sub_resource type="RectangleShape2D" id="RectangleShape2D_26abe"]
-size = Vector2(70, 35)
+size = Vector2(80, 35)
 
 [sub_resource type="CircleShape2D" id="CircleShape2D_0c228"]
 
@@ -359,6 +359,18 @@ tracks/25/keys = {
 "update": 1,
 "values": [false]
 }
+tracks/26/type = "value"
+tracks/26/imported = false
+tracks/26/enabled = true
+tracks/26/path = NodePath("Root/Hitbox:knockback_enabled")
+tracks/26/interp = 1
+tracks/26/loop_wrap = true
+tracks/26/keys = {
+"times": PackedFloat32Array(0),
+"transitions": PackedFloat32Array(1),
+"update": 1,
+"values": [false]
+}
 
 [sub_resource type="Animation" id="Animation_8wj70"]
 resource_name = "attack_1"
@@ -1142,6 +1154,18 @@ tracks/19/keys = {
 "update": 1,
 "values": [true, false, true]
 }
+tracks/20/type = "value"
+tracks/20/imported = false
+tracks/20/enabled = true
+tracks/20/path = NodePath("Root/Hitbox:knockback_enabled")
+tracks/20/interp = 1
+tracks/20/loop_wrap = true
+tracks/20/keys = {
+"times": PackedFloat32Array(0.2, 0.35),
+"transitions": PackedFloat32Array(1, 1),
+"update": 1,
+"values": [true, false]
+}
 
 [sub_resource type="Animation" id="Animation_wei72"]
 resource_name = "death"
@@ -1704,6 +1728,18 @@ tracks/21/keys = {
 "update": 1,
 "values": [false, false]
 }
+tracks/22/type = "value"
+tracks/22/imported = false
+tracks/22/enabled = true
+tracks/22/path = NodePath("Root/Hitbox:knockback_enabled")
+tracks/22/interp = 1
+tracks/22/loop_wrap = true
+tracks/22/keys = {
+"times": PackedFloat32Array(0, 0.25),
+"transitions": PackedFloat32Array(1, 1),
+"update": 1,
+"values": [false, false]
+}
 
 [sub_resource type="Animation" id="Animation_gnqgt"]
 resource_name = "idle"
@@ -3509,9 +3545,8 @@ fixed_fps = 60
 
 [node name="WeaponNinjaStar" type="Sprite2D" parent="Root"]
 visible = false
-position = Vector2(-71.6739, -72.9077)
-rotation = 0.204683
-scale = Vector2(0.999983, 0.999976)
+position = Vector2(-55, -76)
+scale = Vector2(0.999982, 0.999976)
 texture = ExtResource("4_1c5xq")
 
 [node name="Hitbox" type="Area2D" parent="Root"]
@@ -3519,6 +3554,7 @@ position = Vector2(50, 0)
 collision_layer = 0
 collision_mask = 4
 script = ExtResource("5_taq6b")
+knockback_strength = 1000.0
 
 [node name="CollisionShape2D" type="CollisionShape2D" parent="Root/Hitbox"]
 shape = SubResource("RectangleShape2D_2k81i")
diff --git a/demo/demo/agents/player/player.tscn b/demo/demo/agents/player/player.tscn
index 7b24e93..3ae1d03 100644
--- a/demo/demo/agents/player/player.tscn
+++ b/demo/demo/agents/player/player.tscn
@@ -11,6 +11,11 @@ collision_layer = 0
 collision_mask = 1
 script = ExtResource("2_24nyi")
 
+[node name="WeaponNinjaStar" parent="Root" index="2"]
+position = Vector2(-55, -76)
+rotation = 0.0
+scale = Vector2(0.999983, 0.999976)
+
 [node name="Hitbox" parent="Root" index="3"]
 collision_mask = 8
 
diff --git a/demo/demo/agents/player/states/move_state.gd b/demo/demo/agents/player/states/move_state.gd
index 38e60d7..b3c128b 100644
--- a/demo/demo/agents/player/states/move_state.gd
+++ b/demo/demo/agents/player/states/move_state.gd
@@ -27,8 +27,10 @@ func _update(_delta: float) -> void:
 	var horizontal_move: float = Input.get_axis(&"move_left", &"move_right")
 	var vertical_move: float = Input.get_axis(&"move_up", &"move_down")
 
-	agent.velocity = lerp(agent.velocity, Vector2(horizontal_move, vertical_move * VERTICAL_FACTOR) * speed, 0.2)
+	var desired_velocity := Vector2(horizontal_move, vertical_move * VERTICAL_FACTOR) * speed
+	agent.velocity = lerp(agent.velocity, desired_velocity, 0.2)
 	agent.move_and_slide()
+	agent.update_facing()
 
 	if horizontal_move == 0.0 and vertical_move == 0.0:
 		get_root().dispatch(EVENT_FINISHED)
diff --git a/demo/demo/agents/scripts/agent_base.gd b/demo/demo/agents/scripts/agent_base.gd
index 7d86baf..67be03c 100644
--- a/demo/demo/agents/scripts/agent_base.gd
+++ b/demo/demo/agents/scripts/agent_base.gd
@@ -19,6 +19,7 @@ const NinjaStar := preload("res://demo/agents/ninja_star/ninja_star.tscn")
 @onready var root: Node2D = $Root
 @onready var collision_shape_2d: CollisionShape2D = $CollisionShape2D
 
+
 var _frames_since_facing_update: int = 0
 var _is_dead: bool = false
 
@@ -27,11 +28,7 @@ func _ready() -> void:
 	health.death.connect(_die)
 
 
-func _physics_process(_delta: float) -> void:
-	_update_facing()
-
-
-func _update_facing() -> void:
+func update_facing() -> void:
 	_frames_since_facing_update += 1
 	if _frames_since_facing_update > 3:
 		face_dir(velocity.x)
@@ -57,7 +54,8 @@ func throw_ninja_star() -> void:
 	ninja_star.global_position = global_position + Vector2.RIGHT * 100.0 * get_facing()
 
 
-func _damaged(_amount: float) -> void:
+func _damaged(_amount: float, knockback: Vector2) -> void:
+	apply_knockback(knockback)
 	animation_player.play(&"hurt")
 	var btplayer := get_node_or_null(^"BTPlayer") as BTPlayer
 	if btplayer:
@@ -72,8 +70,18 @@ func _damaged(_amount: float) -> void:
 		hsm.set_active(true)
 
 
+func apply_knockback(knockback: Vector2, frames: int = 10) -> void:
+	if knockback.is_zero_approx():
+		return
+	for i in range(frames):
+		velocity = lerp(velocity, knockback, 0.2)
+		move_and_slide()
+		await get_tree().physics_frame
+
+
 func _die() -> void:
 	_is_dead = true
+	root.process_mode = Node.PROCESS_MODE_DISABLED
 	animation_player.play(&"death")
 	collision_shape_2d.set_deferred(&"disabled", true)
 
diff --git a/demo/demo/agents/scripts/health.gd b/demo/demo/agents/scripts/health.gd
index a13f605..ca1b9c4 100644
--- a/demo/demo/agents/scripts/health.gd
+++ b/demo/demo/agents/scripts/health.gd
@@ -14,7 +14,7 @@ extends Node
 
 
 signal death
-signal damaged(amount: float)
+signal damaged(amount: float, knockback: Vector2)
 
 @export var max_health: float = 10.0
 
@@ -25,7 +25,7 @@ func _ready() -> void:
 	_current = max_health
 
 
-func take_damage(amount: float) -> void:
+func take_damage(amount: float, knockback: Vector2) -> void:
 	if _current <= 0.0:
 		return
 
@@ -35,7 +35,7 @@ func take_damage(amount: float) -> void:
 	if _current <= 0.0:
 		death.emit()
 	else:
-		damaged.emit(amount)
+		damaged.emit(amount, knockback)
 
 
 func get_current() -> float:
diff --git a/demo/demo/agents/scripts/hitbox.gd b/demo/demo/agents/scripts/hitbox.gd
index f0b9942..0a34262 100644
--- a/demo/demo/agents/scripts/hitbox.gd
+++ b/demo/demo/agents/scripts/hitbox.gd
@@ -12,14 +12,22 @@ class_name Hitbox
 extends Area2D
 ## Area that deals damage.
 
-
 @export var damage: float = 1.0
-
+@export var knockback_enabled: bool = false
+@export var knockback_strength: float = 500.0
 
 func _ready() -> void:
 	area_entered.connect(_area_entered)
 
 
-func _area_entered(area: Area2D) -> void:
-	var hurtbox := area as Hurtbox
-	hurtbox.take_damage(damage, self)
+func _area_entered(hurtbox: Hurtbox) -> void:
+	if hurtbox.owner == owner:
+		return
+	hurtbox.take_damage(damage, get_knockback())
+
+
+func get_knockback() -> Vector2:
+	var knockback: Vector2
+	if knockback_enabled:
+		knockback = Vector2.RIGHT.rotated(global_rotation) * knockback_strength
+	return knockback
diff --git a/demo/demo/agents/scripts/hurtbox.gd b/demo/demo/agents/scripts/hurtbox.gd
index a10e79b..9c62c6b 100644
--- a/demo/demo/agents/scripts/hurtbox.gd
+++ b/demo/demo/agents/scripts/hurtbox.gd
@@ -16,8 +16,5 @@ extends Area2D
 @export var health: Health
 
 
-func take_damage(amount: float, source: Area2D) -> void:
-	if source.owner == owner:
-		# Don't damage yourself.
-		return
-	health.take_damage(amount)
+func take_damage(amount: float, knockback: Vector2) -> void:
+	health.take_damage(amount, knockback)
diff --git a/demo/demo/ai/tasks/arrive_pos.gd b/demo/demo/ai/tasks/arrive_pos.gd
index efdecc6..63b7394 100644
--- a/demo/demo/ai/tasks/arrive_pos.gd
+++ b/demo/demo/ai/tasks/arrive_pos.gd
@@ -34,6 +34,8 @@ func _tick(_delta: float) -> Status:
 	vertical_factor = clampf(vertical_factor, 0.0, 1.0)
 	var dir: Vector2 = agent.global_position.direction_to(target_pos)
 	dir.y *= vertical_factor
-	agent.velocity = dir.normalized() * speed
+	var desired_velocity: Vector2 = dir.normalized() * speed
+	agent.velocity = lerp(agent.velocity, desired_velocity, 0.2)
 	agent.move_and_slide()
+	agent.update_facing()
 	return RUNNING
diff --git a/demo/demo/ai/tasks/leap_forward.gd b/demo/demo/ai/tasks/leap_forward.gd
index 1f86ca3..6ac32fe 100644
--- a/demo/demo/ai/tasks/leap_forward.gd
+++ b/demo/demo/ai/tasks/leap_forward.gd
@@ -25,8 +25,10 @@ func _generate_name() -> String:
 # Called each time this task is ticked (aka executed).
 func _tick(_delta: float) -> Status:
 	var facing: float = agent.get_facing()
-	agent.velocity = Vector2.RIGHT * facing * force
+	var desired_velocity: Vector2 = Vector2.RIGHT * facing * force
+	agent.velocity = lerp(agent.velocity, desired_velocity, 0.2)
 	agent.move_and_slide()
+	agent.update_facing()
 	if elapsed_time > duration:
 		return SUCCESS
 	return RUNNING
diff --git a/demo/demo/ai/tasks/pursue.gd b/demo/demo/ai/tasks/pursue.gd
index ede859f..a08b6d2 100644
--- a/demo/demo/ai/tasks/pursue.gd
+++ b/demo/demo/ai/tasks/pursue.gd
@@ -50,8 +50,10 @@ func _tick(_delta: float) -> Status:
 	var speed: float = blackboard.get_var(speed_var, 200.0)
 	if agent.global_position.distance_to(_waypoint) < TOLERANCE:
 		_select_new_waypoint(desired_pos)
-	agent.velocity = agent.global_position.direction_to(_waypoint) * speed
+	var desired_velocity: Vector2 = agent.global_position.direction_to(_waypoint) * speed
+	agent.velocity = lerp(agent.velocity, desired_velocity, 0.2)
 	agent.move_and_slide()
+	agent.update_facing()
 	return RUNNING