Add fallback camera with mouse controls

project/aircraft/aircraft.gd

@@ -1,5 +1,7 @@
 extends Node3D
 
+signal use_fallback(active: bool)
+
 ## Rotation of cyclic stick model for full control deflection, in degrees
 @export var range_cyclic: float = 30
 ## Main rotor speed, in revolutions per minute
@@ -16,6 +18,7 @@ var _rotor_azimuth: float = 0
 @onready var tracker_mount_platform: Node3D = $AttitudeRoot/PilotEyes/PilotFloor/TrackerMountPlatform
 @onready var xr_origin: XROrigin3D = $AttitudeRoot/PilotEyes/PilotFloor/XROrigin3D
 @onready var tracker: XRController3D = $AttitudeRoot/PilotEyes/PilotFloor/XROrigin3D/ViveTracker
+@onready var xr_camera: XRCamera3D = $AttitudeRoot/PilotEyes/PilotFloor/XROrigin3D/XRCamera3D
 
 @onready var bone_cg: int = skeleton.find_bone("BodyCG")
 @onready var bone_cyclic: int = skeleton.find_bone("Cyclic")
@@ -53,3 +56,7 @@ func _process(delta: float) -> void:
 		xr_origin.transform = tracker_mount.transform * tracker.transform.affine_inverse()
 	else:
 		xr_origin.transform = Transform3D.IDENTITY
+
+func _on_vr_setup_failed() -> void:
+	xr_camera.current = false
+	use_fallback.emit(true)

project/aircraft/aircraft.tscn

@@ -1,9 +1,10 @@
-[gd_scene load_steps=6 format=3 uid="uid://bj1s0g7ixjw71"]
+[gd_scene load_steps=7 format=3 uid="uid://bj1s0g7ixjw71"]
 
 [ext_resource type="Script" uid="uid://cx30pr7kn4c74" path="res://aircraft/aircraft.gd" id="1_l4uib"]
 [ext_resource type="PackedScene" uid="uid://cux4tju0ovvly" path="res://assets/mi2/Mi-2.glb" id="1_mrxe8"]
 [ext_resource type="PackedScene" uid="uid://fmygcraoturj" path="res://reference_axes.tscn" id="3_2bi7g"]
 [ext_resource type="PackedScene" uid="uid://cis4s43ubuynp" path="res://instruments.tscn" id="3_5w717"]
+[ext_resource type="Script" uid="uid://bt32fse84itrp" path="res://aircraft/fallback_input.gd" id="3_gf6ud"]
 
 [sub_resource type="StandardMaterial3D" id="StandardMaterial3D_mrxe8"]
 
@@ -22,6 +23,7 @@ transform = Transform3D(1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 2.4, 0)
 [node name="PilotEyes" type="Node3D" parent="AttitudeRoot"]
 editor_description = "Target position for Local XR tracking"
 transform = Transform3D(-1, 0, -8.74228e-08, 0, 1, 0, 8.74228e-08, 0, -1, 0.214, -0.7, 1.594)
+script = ExtResource("3_gf6ud")
 
 [node name="PilotFloor" type="Node3D" parent="AttitudeRoot/PilotEyes"]
 editor_description = "Required for floor tracking
@@ -44,6 +46,7 @@ visible = false
 [node name="XROrigin3D" type="XROrigin3D" parent="AttitudeRoot/PilotEyes/PilotFloor"]
 
 [node name="XRCamera3D" type="XRCamera3D" parent="AttitudeRoot/PilotEyes/PilotFloor/XROrigin3D"]
+current = true
 
 [node name="ViveTracker" type="XRController3D" parent="AttitudeRoot/PilotEyes/PilotFloor/XROrigin3D"]
 tracker = &"/user/vive_tracker_htcx/role/camera"
@@ -52,9 +55,14 @@ tracker = &"/user/vive_tracker_htcx/role/camera"
 transform = Transform3D(0.25, 0, 0, 0, 0.25, 0, 0, 0, 0.25, 0, 0, 0)
 visible = false
 
+[node name="FallbackCamera" type="Camera3D" parent="AttitudeRoot/PilotEyes"]
+transform = Transform3D(1, 0, 0, 0, 0.980955, 0.194234, 0, -0.194234, 0.980955, 0, 0, 0)
+
 [node name="Instruments" parent="AttitudeRoot" instance=ExtResource("3_5w717")]
 transform = Transform3D(-0.5, -1.27582e-08, 7.43353e-08, 4.33325e-10, 0.4923, 0.0874084, -7.5421e-08, 0.0874084, -0.4923, 0.00724897, -1.1581, 2.40391)
 
 [node name="MarshConnector" type="MarshConnector" parent="."]
 
+[connection signal="use_fallback" from="." to="AttitudeRoot/PilotEyes" method="_on_aircraft_use_fallback"]
+
 [editable path="Mi-2"]

project/aircraft/fallback_input.gd

@@ -0,0 +1,58 @@
+# Based on Godot Engine Third Person Shooter Demo, used under MIT License
+# Copyright (c) 2018-2021 Juan Linietsky, Godot Engine contributors
+# https://github.com/godotengine/tps-demo/blob/master/player/player_input.gd
+
+extends Node3D
+
+const CAMERA_MOUSE_ROTATION_SPEED := 0.001
+const CAMERA_X_ROT_MIN := deg_to_rad(-85)
+const CAMERA_X_ROT_MAX := deg_to_rad(70)
+
+var active: bool = false
+var initial_rotation: Vector3
+
+@onready var camera_base = $"."
+@onready var camera = $FallbackCamera
+
+func _ready() -> void:
+	set_process(false)
+	set_process_input(false)
+	initial_rotation = camera.rotation
+
+func _on_aircraft_use_fallback(active_in: bool) -> void:
+	if active_in:
+		set_process(true)
+		set_process_input(true)
+		camera.make_current()
+		Input.set_mouse_mode(Input.MOUSE_MODE_CAPTURED)
+	else:
+		set_process(false)
+		set_process_input(false)
+		camera.current = false
+		Input.set_mouse_mode(Input.MOUSE_MODE_VISIBLE) # default value
+
+		# Reset the rotation
+		camera_base.rotation = Vector3.ZERO
+		camera.rotation = initial_rotation
+
+	active = active_in
+
+
+func _input(event):
+	# Make mouse aiming speed resolution-independent
+	# (required when using the `canvas_items` stretch mode).
+	var scale_factor: float = min(
+			(float(get_viewport().size.x) / get_viewport().get_visible_rect().size.x),
+			(float(get_viewport().size.y) / get_viewport().get_visible_rect().size.y)
+	)
+
+	if event is InputEventMouseMotion:
+		var camera_speed_this_frame = CAMERA_MOUSE_ROTATION_SPEED
+		rotate_camera(event.relative * camera_speed_this_frame * scale_factor)
+
+
+func rotate_camera(move):
+	camera_base.rotate_y(-move.x)
+	# After relative transforms, camera needs to be renormalized.
+	camera_base.orthonormalize()
+	camera.rotation.x = clamp(camera.rotation.x - move.y, CAMERA_X_ROT_MIN, CAMERA_X_ROT_MAX)

project/aircraft/fallback_input.gd.uid

@@ -0,0 +1 @@
+uid://bt32fse84itrp

project/main.tscn

@@ -28,3 +28,5 @@ shadow_enabled = true
 
 [node name="StartVR" type="Node3D" parent="."]
 script = ExtResource("1_ig7tw")
+
+[connection signal="setup_failed" from="StartVR" to="Aircraft" method="_on_vr_setup_failed"]

project/start_vr.gd

@@ -3,6 +3,7 @@ extends Node3D
 signal focus_lost
 signal focus_gained
 signal pose_recentered
+signal setup_failed
 
 @export var maximum_refresh_rate : int = 90
 
@@ -40,6 +41,7 @@ func _ready() -> void:
 		print("OpenXR not instantiated!")
 		# Allow the game to run without VR
 		#get_tree().quit()
+		setup_failed.emit()
 
 
 func _on_tracker_added(tracker_name: StringName, type: int) -> void: