feat: add spectator camera flag

Signed-off-by: Schmarni <marnistromer@gmail.com>

src/main.rs

@@ -5,12 +5,14 @@ mod core;
 mod nodes;
 mod objects;
 mod session;
+mod spectator_cam;
 pub mod tracking_offset;
 #[cfg(feature = "wayland")]
 mod wayland;
 
 use crate::nodes::drawable::sky::SkyPlugin;
 use crate::nodes::input;
+use crate::spectator_cam::SpectatorCameraPlugin;
 
 use bevy::MinimalPlugins;
 use bevy::a11y::AccessibilityPlugin;
@@ -89,6 +91,10 @@ struct CliArgs {
 	#[clap(short, long, action)]
 	flatscreen: bool,
 
+	/// Replaces the flatscreen mode with a first person spectator camera
+	#[clap(short, long, action)]
+	spectator: bool,
+
 	/// Creates a transparent window fot the flatscreen mode
 	#[clap(short, long, action)]
 	transparent_flatscreen: bool,
@@ -326,10 +332,11 @@ fn bevy_loop(
 	{
 		let mut plugin = WinitPlugin::<WakeUp>::default();
 		plugin.run_on_any_thread = true;
-		plugins = plugins
-			.add(plugin)
-			.disable::<ScheduleRunnerPlugin>()
-			.add(FlatscreenInputPlugin);
+		plugins = plugins.add(plugin).disable::<ScheduleRunnerPlugin>();
+		plugins = match args.spectator {
+			true => plugins.add(SpectatorCameraPlugin),
+			false => plugins.add(FlatscreenInputPlugin),
+		};
 	}
 	app.add_plugins(
 		if !args.flatscreen {

src/spectator_cam.rs

@@ -0,0 +1,39 @@
+use bevy::{
+	app::Plugin,
+	core_pipeline::core_3d::Camera3d,
+	ecs::{
+		component::Component,
+		system::{Commands, Res},
+	},
+	render::camera::{PerspectiveProjection, Projection},
+	transform::components::Transform,
+};
+use bevy_mod_openxr::session::OxrSession;
+use bevy_mod_xr::session::XrSessionCreated;
+use openxr::ReferenceSpaceType;
+
+pub struct SpectatorCameraPlugin;
+
+impl Plugin for SpectatorCameraPlugin {
+	fn build(&self, app: &mut bevy::app::App) {
+		app.add_systems(XrSessionCreated, create);
+	}
+}
+
+#[derive(Component)]
+#[require(Camera3d)]
+struct SpectatorCam;
+
+fn create(session: Res<OxrSession>, mut cmds: Commands) {
+	cmds.spawn((
+		SpectatorCam,
+		session
+			.create_reference_space(ReferenceSpaceType::VIEW, Transform::IDENTITY)
+			.unwrap()
+			.0,
+		Projection::Perspective(PerspectiveProjection {
+			fov: 100f32.to_radians(),
+			..Default::default()
+		}),
+	));
+}