Nicer usage for scene viewer (#7035)

# Objective
Scene viewer mouse sensitivity/cursor usage isn't the best it could be atm, so just adding some quick, maybe opinionated, tweaks to make it feel more at home in usage.

## Solution
- Mouse delta shouldn't be affected by delta time, it should be more expected that if I move my mouse 1 inch to the right that it should move the in game camera/whatever is controlled the same regardless of FPS.
- Uses a magic number of 180.0 for a nice default sensitivity, modeled after Valorant's default sensitivity.
- Cursor now gets locked/hidden when rotating the camera to give it more of the effect that you are grabbing the camera.

examples/tools/scene_viewer/camera_controller_plugin.rs

@@ -3,11 +3,17 @@
 //! - Copy the code for the `CameraControllerPlugin` and add the plugin to your App.
 //! - Attach the `CameraController` component to an entity with a `Camera3dBundle`.
 
+use bevy::window::CursorGrabMode;
 use bevy::{input::mouse::MouseMotion, prelude::*};
 
 use std::f32::consts::*;
 use std::fmt;
 
+/// Based on Valorant's default sensitivity, not entirely sure why it is exactly 1.0 / 180.0,
+/// but I'm guessing it is a misunderstanding between degrees/radians and then sticking with
+/// it because it felt nice.
+pub const RADIANS_PER_DOT: f32 = 1.0 / 180.0;
+
 #[derive(Component)]
 pub struct CameraController {
     pub enabled: bool,
@@ -35,7 +41,7 @@ impl Default for CameraController {
         Self {
             enabled: true,
             initialized: false,
-            sensitivity: 0.5,
+            sensitivity: 1.0,
             key_forward: KeyCode::W,
             key_back: KeyCode::S,
             key_left: KeyCode::A,
@@ -91,12 +97,14 @@ impl Plugin for CameraControllerPlugin {
 
 fn camera_controller(
     time: Res<Time>,
+    mut windows: ResMut<Windows>,
     mut mouse_events: EventReader<MouseMotion>,
     mouse_button_input: Res<Input<MouseButton>>,
     key_input: Res<Input<KeyCode>>,
     mut move_toggled: Local<bool>,
     mut query: Query<(&mut Transform, &mut CameraController), With<Camera>>,
 ) {
+    let window = windows.primary_mut();
     let dt = time.delta_seconds();
 
     if let Ok((mut transform, mut options)) = query.get_single_mut() {
@@ -158,16 +166,22 @@ fn camera_controller(
         // Handle mouse input
         let mut mouse_delta = Vec2::ZERO;
         if mouse_button_input.pressed(options.mouse_key_enable_mouse) || *move_toggled {
+            window.set_cursor_grab_mode(CursorGrabMode::Locked);
+            window.set_cursor_visibility(false);
+
             for mouse_event in mouse_events.iter() {
                 mouse_delta += mouse_event.delta;
             }
+        } else {
+            window.set_cursor_grab_mode(CursorGrabMode::None);
+            window.set_cursor_visibility(true);
         }
 
         if mouse_delta != Vec2::ZERO {
             // Apply look update
-            options.pitch = (options.pitch - mouse_delta.y * 0.5 * options.sensitivity * dt)
+            options.pitch = (options.pitch - mouse_delta.y * RADIANS_PER_DOT * options.sensitivity)
                 .clamp(-PI / 2., PI / 2.);
-            options.yaw -= mouse_delta.x * options.sensitivity * dt;
+            options.yaw -= mouse_delta.x * RADIANS_PER_DOT * options.sensitivity;
             transform.rotation = Quat::from_euler(EulerRot::ZYX, 0.0, options.yaw, options.pitch);
         }
     }