Add shake effect on shooting.

based on youtube.com/watch?v=tu-Qe66AvtY (Squirrel Eiserloh, Math for Game Programmers: Juicing Your Cameras With Math, GDC 2016)
Thanks to asheraryam

player/camera_noise_shake_effect.gd

@@ -0,0 +1,63 @@
+extends Camera
+
+# Constant values of the effect.
+const SPEED = 1.0
+const DECAY_RATE = 1.5
+const MAX_YAW = 0.05
+const MAX_PITCH = 0.05
+const MAX_ROLL = 0.1
+const MAX_TRAUMA = 0.6
+
+# Default values.
+var start_rotation = rotation
+var trauma = 0.0
+var time = 0.0
+var noise = OpenSimplexNoise.new()
+var noise_seed = randi()
+
+
+func _ready():
+	noise.seed = noise_seed
+	noise.octaves = 1
+	noise.period = 256.0
+	noise.persistence = 0.5
+	noise.lacunarity = 1.0
+	
+	# This variable is reset if the camera position is changed by other scripts,
+	# such as when zooming in/out or focusing on a different position.
+	# This should NOT be done when the camera shake is happening.
+	start_rotation = rotation
+
+
+func _process(delta):
+	if trauma > 0.0:
+		decay_trauma(delta)
+		apply_shake(delta)
+
+
+# Add trauma to start/continue the shake.
+func add_trauma(amount):
+	trauma = min(trauma + amount, MAX_TRAUMA)
+
+
+# Decay the trauma effect over time.
+func decay_trauma(delta):
+	var change = DECAY_RATE * delta
+	trauma = max(trauma - change, 0.0)
+
+
+# Apply the random shake accoring to delta time.
+func apply_shake(delta):
+	# Using a magic number here to get a pleasing effect at SPEED 1.0.
+	time += delta * SPEED * 5000.0
+	var shake = trauma * trauma
+	var yaw = MAX_YAW * shake * get_noise_value(noise_seed, time)
+	var pitch = MAX_PITCH * shake * get_noise_value(noise_seed + 1, time)
+	var roll = MAX_ROLL * shake * get_noise_value(noise_seed + 2, time)
+	rotation = start_rotation + Vector3(pitch, yaw, roll)
+
+
+# Return a random float in range(-1, 1) using OpenSimplex noise.
+func get_noise_value(seed_value, t):
+	noise.seed = seed_value
+	return noise.get_noise_1d(t)

player/player.gd

@@ -159,6 +159,8 @@ func _physics_process(delta):
 			bullet.add_collision_exception_with(self)
 			fire_cooldown.start()
 			sound_effect_shoot.play()
+			camera_camera.add_trauma(0.35)
+
 	else: # Not in air or aiming, idle.
 		# Convert orientation to quaternions for interpolating rotation.
 		var target = camera_x * motion.x + camera_z * motion.y

player/player.tscn

@@ -1,4 +1,4 @@
-[gd_scene load_steps=35 format=2]
+[gd_scene load_steps=36 format=2]
 
 [ext_resource path="res://player/player.gd" type="Script" id=1]
 [ext_resource path="res://player/model/player.dae" type="PackedScene" id=2]
@@ -7,6 +7,7 @@
 [ext_resource path="res://player/audio/jump.wav" type="AudioStream" id=5]
 [ext_resource path="res://player/audio/land.wav" type="AudioStream" id=6]
 [ext_resource path="res://player/audio/shoot.wav" type="AudioStream" id=7]
+[ext_resource path="res://player/camera_noise_shake_effect.gd" type="Script" id=8]
 
 [sub_resource type="AnimationNodeAdd3" id=1]
 resource_local_to_scene = true
@@ -152,7 +153,7 @@ nodes/strafe/node = SubResource( 16 )
 nodes/strafe/position = Vector2( -400, -120 )
 nodes/walk/node = SubResource( 21 )
 nodes/walk/position = Vector2( -400, 40 )
-node_connections = [ "output", 0, "eye_blend", "state", 0, "strafe", "state", 1, "walk", "state", 2, "jumpup", "state", 3, "jumpdown", "land", 0, "state", "land", 1, "hardland", "aim", 0, "aimdown", "aim", 1, "land", "aim", 2, "aimup", "eye_blend", 0, "aim", "eye_blend", 1, "eyes" ]
+node_connections = [ "output", 0, "eye_blend", "state", 0, "strafe", "state", 1, "walk", "state", 2, "jumpup", "state", 3, "jumpdown", "aim", 0, "aimdown", "aim", 1, "land", "aim", 2, "aimup", "eye_blend", 0, "aim", "eye_blend", 1, "eyes", "land", 0, "state", "land", 1, "hardland" ]
 
 [sub_resource type="CapsuleShape" id=23]
 radius = 0.5
@@ -229,7 +230,7 @@ transform = Transform( 0.803991, 0, 0, 0, 0.803991, 0, 0, 0, 0.803991, 0, 0, 0 )
 bones/46/bound_children = [ NodePath("GunBone") ]
 
 [node name="GunBone" type="BoneAttachment" parent="PlayerModel/Robot_Skeleton/Skeleton" index="5"]
-transform = Transform( 0.916368, -0.24167, 0.319464, -0.240673, -0.969661, -0.0435164, 0.320323, -0.0369838, -0.946598, -0.207126, 1.38922, 0.483314 )
+transform = Transform( 0.904321, -0.247813, 0.347821, -0.25677, -0.966275, -0.0211712, 0.341372, -0.0701338, -0.937322, -0.207136, 1.3677, 0.535182 )
 bone_name = "hand.R"
 
 [node name="ShootFrom" type="Position3D" parent="PlayerModel/Robot_Skeleton/Skeleton/GunBone"]
@@ -278,6 +279,7 @@ spring_length = 2.4
 transform = Transform( 1, 1.42109e-14, -2.84217e-14, 0, 1, 0, 0, 0, 1, 0, 0, 0 )
 current = true
 far = 300.0
+script = ExtResource( 8 )
 __meta__ = {
 "_editor_description_": "Translated when aiming."
 }