From 8e7ef64bb16347ea0258ac66790f950cacd04d7b Mon Sep 17 00:00:00 2001
From: Rich Churcher <rich.churcher@gmail.com>
Date: Wed, 11 Sep 2024 11:40:48 +1200
Subject: [PATCH] Split zoom/orbit into separate examples (#15135)

# Objective

As previously discussed, split camera zoom and orbiting examples to keep
things less cluttered. See discussion on #15092 for context.
---
 Cargo.toml                         |  13 ++-
 examples/README.md                 |   3 +-
 examples/camera/camera_orbit.rs    | 163 +++++++++++++++++++++++++++++
 examples/camera/projection_zoom.rs |  82 +++------------
 4 files changed, 189 insertions(+), 72 deletions(-)
 create mode 100644 examples/camera/camera_orbit.rs

diff --git a/Cargo.toml b/Cargo.toml
index 634ef2391d..0609e02c33 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -3251,7 +3251,18 @@ doc-scrape-examples = true
 
 [package.metadata.example.projection_zoom]
 name = "Projection Zoom"
-description = "Shows how to zoom and orbit orthographic and perspective projection cameras."
+description = "Shows how to zoom orthographic and perspective projection cameras."
+category = "Camera"
+wasm = true
+
+[[example]]
+name = "camera_orbit"
+path = "examples/camera/camera_orbit.rs"
+doc-scrape-examples = true
+
+[package.metadata.example.camera_orbit]
+name = "Camera Orbit"
+description = "Shows how to orbit a static scene using pitch, yaw, and roll."
 category = "Camera"
 wasm = true
 
diff --git a/examples/README.md b/examples/README.md
index 542a827640..92e03582aa 100644
--- a/examples/README.md
+++ b/examples/README.md
@@ -254,8 +254,9 @@ Example | Description
 Example | Description
 --- | ---
 [2D top-down camera](../examples/camera/2d_top_down_camera.rs) | A 2D top-down camera smoothly following player movements
+[Camera Orbit](../examples/camera/camera_orbit.rs) | Shows how to orbit a static scene using pitch, yaw, and roll.
 [First person view model](../examples/camera/first_person_view_model.rs) | A first-person camera that uses a world model and a view model with different field of views (FOV)
-[Projection Zoom](../examples/camera/projection_zoom.rs) | Shows how to zoom and orbit orthographic and perspective projection cameras.
+[Projection Zoom](../examples/camera/projection_zoom.rs) | Shows how to zoom orthographic and perspective projection cameras.
 
 ## Dev tools
 
diff --git a/examples/camera/camera_orbit.rs b/examples/camera/camera_orbit.rs
new file mode 100644
index 0000000000..c0e80e636a
--- /dev/null
+++ b/examples/camera/camera_orbit.rs
@@ -0,0 +1,163 @@
+//! Shows how to orbit camera around a static scene using pitch, yaw, and roll.
+
+use std::{f32::consts::FRAC_PI_2, ops::Range};
+
+use bevy::prelude::*;
+
+#[derive(Debug, Default, Resource)]
+struct CameraSettings {
+    pub orbit_distance: f32,
+    // Multiply keyboard inputs by this factor
+    pub orbit_speed: f32,
+    // Clamp pitch to this range
+    pub pitch_range: Range<f32>,
+}
+
+fn main() {
+    App::new()
+        .add_plugins(DefaultPlugins)
+        .init_resource::<CameraSettings>()
+        .add_systems(Startup, (setup, instructions))
+        .add_systems(Update, orbit)
+        .run();
+}
+
+/// Set up a simple 3D scene
+fn setup(
+    mut camera_settings: ResMut<CameraSettings>,
+    mut commands: Commands,
+    mut meshes: ResMut<Assets<Mesh>>,
+    mut materials: ResMut<Assets<StandardMaterial>>,
+) {
+    // Limiting pitch stops some unexpected rotation past 90° up or down.
+    let pitch_limit = FRAC_PI_2 - 0.01;
+
+    camera_settings.orbit_distance = 10.0;
+    camera_settings.orbit_speed = 1.0;
+    camera_settings.pitch_range = -pitch_limit..pitch_limit;
+
+    commands.spawn((
+        Name::new("Camera"),
+        Camera3dBundle {
+            transform: Transform::from_xyz(5.0, 5.0, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
+            ..default()
+        },
+    ));
+
+    commands.spawn((
+        Name::new("Plane"),
+        PbrBundle {
+            mesh: meshes.add(Plane3d::default().mesh().size(5.0, 5.0)),
+            material: materials.add(StandardMaterial {
+                base_color: Color::srgb(0.3, 0.5, 0.3),
+                // Turning off culling keeps the plane visible when viewed from beneath.
+                cull_mode: None,
+                ..default()
+            }),
+            ..default()
+        },
+    ));
+
+    commands.spawn((
+        Name::new("Cube"),
+        PbrBundle {
+            mesh: meshes.add(Cuboid::default()),
+            material: materials.add(Color::srgb(0.8, 0.7, 0.6)),
+            transform: Transform::from_xyz(1.5, 0.51, 1.5),
+            ..default()
+        },
+    ));
+
+    commands.spawn((
+        Name::new("Light"),
+        PointLightBundle {
+            transform: Transform::from_xyz(3.0, 8.0, 5.0),
+            ..default()
+        },
+    ));
+}
+
+fn instructions(mut commands: Commands) {
+    commands
+        .spawn((
+            Name::new("Instructions"),
+            NodeBundle {
+                style: Style {
+                    align_items: AlignItems::Start,
+                    flex_direction: FlexDirection::Column,
+                    justify_content: JustifyContent::Start,
+                    width: Val::Percent(100.),
+                    ..default()
+                },
+                ..default()
+            },
+        ))
+        .with_children(|parent| {
+            parent.spawn(TextBundle::from_section(
+                "W or S: pitch",
+                TextStyle::default(),
+            ));
+            parent.spawn(TextBundle::from_section(
+                "A or D: yaw",
+                TextStyle::default(),
+            ));
+            parent.spawn(TextBundle::from_section(
+                "Q or E: roll",
+                TextStyle::default(),
+            ));
+        });
+}
+
+fn orbit(
+    mut camera: Query<&mut Transform, With<Camera>>,
+    camera_settings: Res<CameraSettings>,
+    keyboard_input: Res<ButtonInput<KeyCode>>,
+    time: Res<Time>,
+) {
+    let mut transform = camera.single_mut();
+
+    let mut delta_pitch = 0.0;
+    let mut delta_roll = 0.0;
+    let mut delta_yaw = 0.0;
+
+    if keyboard_input.pressed(KeyCode::KeyW) {
+        delta_pitch += camera_settings.orbit_speed;
+    }
+    if keyboard_input.pressed(KeyCode::KeyS) {
+        delta_pitch -= camera_settings.orbit_speed;
+    }
+
+    if keyboard_input.pressed(KeyCode::KeyQ) {
+        delta_roll -= camera_settings.orbit_speed;
+    }
+    if keyboard_input.pressed(KeyCode::KeyE) {
+        delta_roll += camera_settings.orbit_speed;
+    }
+
+    if keyboard_input.pressed(KeyCode::KeyA) {
+        delta_yaw -= camera_settings.orbit_speed;
+    }
+    if keyboard_input.pressed(KeyCode::KeyD) {
+        delta_yaw += camera_settings.orbit_speed;
+    }
+
+    // Incorporating the delta time between calls prevents this from being framerate-bound.
+    delta_pitch *= time.delta_seconds();
+    delta_roll *= time.delta_seconds();
+    delta_yaw *= time.delta_seconds();
+
+    // Obtain the existing pitch, yaw, and roll values from the transform.
+    let (yaw, pitch, roll) = transform.rotation.to_euler(EulerRot::YXZ);
+
+    // Establish the new yaw and pitch, preventing the pitch value from exceeding our limits.
+    let pitch = (pitch + delta_pitch).clamp(
+        camera_settings.pitch_range.start,
+        camera_settings.pitch_range.end,
+    );
+    let roll = roll + delta_roll;
+    let yaw = yaw + delta_yaw;
+    transform.rotation = Quat::from_euler(EulerRot::YXZ, yaw, pitch, roll);
+
+    // Adjust the translation to maintain the correct orientation toward the orbit target.
+    transform.translation = Vec3::ZERO - transform.forward() * camera_settings.orbit_distance;
+}
diff --git a/examples/camera/projection_zoom.rs b/examples/camera/projection_zoom.rs
index d490d971b8..108567ab55 100644
--- a/examples/camera/projection_zoom.rs
+++ b/examples/camera/projection_zoom.rs
@@ -1,17 +1,11 @@
-//! Shows how to zoom and orbit orthographic and perspective projection cameras.
+//! Shows how to zoom orthographic and perspective projection cameras.
 
-use std::{
-    f32::consts::{FRAC_PI_2, PI},
-    ops::Range,
-};
+use std::{f32::consts::PI, ops::Range};
 
 use bevy::{input::mouse::AccumulatedMouseScroll, prelude::*, render::camera::ScalingMode};
 
 #[derive(Debug, Default, Resource)]
 struct CameraSettings {
-    pub orbit_distance: f32,
-    // Multiply keyboard inputs by this factor
-    pub orbit_speed: f32,
     // Clamp fixed vertical scale to this range
     pub orthographic_zoom_range: Range<f32>,
     // Multiply mouse wheel inputs by this factor
@@ -20,8 +14,6 @@ struct CameraSettings {
     pub perspective_zoom_range: Range<f32>,
     // Multiply mouse wheel inputs by this factor
     pub perspective_zoom_speed: f32,
-    // Clamp pitch to this range
-    pub pitch_range: Range<f32>,
 }
 
 fn main() {
@@ -29,12 +21,13 @@ fn main() {
         .add_plugins(DefaultPlugins)
         .init_resource::<CameraSettings>()
         .add_systems(Startup, (setup, instructions))
-        .add_systems(Update, (orbit, switch_projection, zoom))
+        .add_systems(Update, (switch_projection, zoom))
         .run();
 }
 
 /// Set up a simple 3D scene
 fn setup(
+    asset_server: Res<AssetServer>,
     mut camera_settings: ResMut<CameraSettings>,
     mut commands: Commands,
     mut meshes: ResMut<Assets<Mesh>>,
@@ -51,17 +44,11 @@ fn setup(
     let min_zoom = 5.0;
     let max_zoom = 150.0;
 
-    // Limiting pitch stops some unexpected rotation past 90° up or down.
-    let pitch_limit = FRAC_PI_2 - 0.01;
-
-    camera_settings.orbit_distance = 10.0;
-    camera_settings.orbit_speed = 1.0;
     camera_settings.orthographic_zoom_range = min_zoom..max_zoom;
     camera_settings.orthographic_zoom_speed = 1.0;
     camera_settings.perspective_zoom_range = min_fov..max_fov;
     // Changes in FOV are much more noticeable due to its limited range in radians
     camera_settings.perspective_zoom_speed = 0.05;
-    camera_settings.pitch_range = -pitch_limit..pitch_limit;
 
     commands.spawn((
         Name::new("Camera"),
@@ -93,11 +80,13 @@ fn setup(
     ));
 
     commands.spawn((
-        Name::new("Cube"),
-        PbrBundle {
-            mesh: meshes.add(Cuboid::default()),
-            material: materials.add(Color::srgb(0.8, 0.7, 0.6)),
-            transform: Transform::from_xyz(1.5, 0.51, 1.5),
+        Name::new("Fox"),
+        SceneBundle {
+            scene: asset_server
+                .load(GltfAssetLabel::Scene(0).from_asset("models/animated/Fox.glb")),
+            // Note: the scale adjustment is purely an accident of our fox model, which renders
+            // HUGE unless mitigated!
+            transform: Transform::from_translation(Vec3::splat(0.0)).with_scale(Vec3::splat(0.025)),
             ..default()
         },
     ));
@@ -132,59 +121,12 @@ fn instructions(mut commands: Commands) {
                 TextStyle::default(),
             ));
             parent.spawn(TextBundle::from_section(
-                "W or S: pitch",
-                TextStyle::default(),
-            ));
-            parent.spawn(TextBundle::from_section(
-                "A or D: yaw",
+                "Space: switch between orthographic and perspective projections",
                 TextStyle::default(),
             ));
         });
 }
 
-fn orbit(
-    mut camera: Query<&mut Transform, With<Camera>>,
-    camera_settings: Res<CameraSettings>,
-    keyboard_input: Res<ButtonInput<KeyCode>>,
-    time: Res<Time>,
-) {
-    let mut transform = camera.single_mut();
-
-    let mut delta_pitch = 0.0;
-    let mut delta_yaw = 0.0;
-
-    if keyboard_input.pressed(KeyCode::KeyW) {
-        delta_pitch += camera_settings.orbit_speed;
-    }
-    if keyboard_input.pressed(KeyCode::KeyA) {
-        delta_yaw -= camera_settings.orbit_speed;
-    }
-    if keyboard_input.pressed(KeyCode::KeyS) {
-        delta_pitch -= camera_settings.orbit_speed;
-    }
-    if keyboard_input.pressed(KeyCode::KeyD) {
-        delta_yaw += camera_settings.orbit_speed;
-    }
-
-    // Incorporating the delta time between calls prevents this from being framerate-bound.
-    delta_pitch *= time.delta_seconds();
-    delta_yaw *= time.delta_seconds();
-
-    // Obtain the existing pitch, yaw, and roll values from the transform.
-    let (yaw, pitch, roll) = transform.rotation.to_euler(EulerRot::YXZ);
-
-    // Establish the new yaw and pitch, preventing the pitch value from exceeding our limits.
-    let pitch = (pitch + delta_pitch).clamp(
-        camera_settings.pitch_range.start,
-        camera_settings.pitch_range.end,
-    );
-    let yaw = yaw + delta_yaw;
-    transform.rotation = Quat::from_euler(EulerRot::YXZ, yaw, pitch, roll);
-
-    // Adjust the translation to maintain the correct orientation toward the orbit target.
-    transform.translation = Vec3::ZERO - transform.forward() * camera_settings.orbit_distance;
-}
-
 fn switch_projection(
     mut camera: Query<&mut Projection, With<Camera>>,
     camera_settings: Res<CameraSettings>,