camera_orbit/
camera_orbit.rs

1//! Shows how to orbit camera around a static scene using pitch, yaw, and roll.
2//!
3//! See also: `first_person_view_model` example, which does something similar but as a first-person
4//! camera view.
5
6use std::{f32::consts::FRAC_PI_2, ops::Range};
7
8use bevy::{input::mouse::AccumulatedMouseMotion, prelude::*};
9
10#[derive(Debug, Resource)]
11struct CameraSettings {
12    pub orbit_distance: f32,
13    pub pitch_speed: f32,
14    // Clamp pitch to this range
15    pub pitch_range: Range<f32>,
16    pub roll_speed: f32,
17    pub yaw_speed: f32,
18}
19
20impl Default for CameraSettings {
21    fn default() -> Self {
22        // Limiting pitch stops some unexpected rotation past 90° up or down.
23        let pitch_limit = FRAC_PI_2 - 0.01;
24        Self {
25            // These values are completely arbitrary, chosen because they seem to produce
26            // "sensible" results for this example. Adjust as required.
27            orbit_distance: 20.0,
28            pitch_speed: 0.003,
29            pitch_range: -pitch_limit..pitch_limit,
30            roll_speed: 1.0,
31            yaw_speed: 0.004,
32        }
33    }
34}
35
36fn main() {
37    App::new()
38        .add_plugins(DefaultPlugins)
39        .init_resource::<CameraSettings>()
40        .add_systems(Startup, (setup, instructions))
41        .add_systems(Update, orbit)
42        .run();
43}
44
45/// Set up a simple 3D scene
46fn setup(
47    mut commands: Commands,
48    mut meshes: ResMut<Assets<Mesh>>,
49    mut materials: ResMut<Assets<StandardMaterial>>,
50) {
51    commands.spawn((
52        Name::new("Camera"),
53        Camera3d::default(),
54        Transform::from_xyz(5.0, 5.0, 5.0).looking_at(Vec3::ZERO, Vec3::Y),
55    ));
56
57    commands.spawn((
58        Name::new("Plane"),
59        Mesh3d(meshes.add(Plane3d::default().mesh().size(5.0, 5.0))),
60        MeshMaterial3d(materials.add(StandardMaterial {
61            base_color: Color::srgb(0.3, 0.5, 0.3),
62            // Turning off culling keeps the plane visible when viewed from beneath.
63            cull_mode: None,
64            ..default()
65        })),
66    ));
67
68    commands.spawn((
69        Name::new("Cube"),
70        Mesh3d(meshes.add(Cuboid::default())),
71        MeshMaterial3d(materials.add(Color::srgb(0.8, 0.7, 0.6))),
72        Transform::from_xyz(1.5, 0.51, 1.5),
73    ));
74
75    commands.spawn((
76        Name::new("Light"),
77        PointLight::default(),
78        Transform::from_xyz(3.0, 8.0, 5.0),
79    ));
80}
81
82fn instructions(mut commands: Commands) {
83    commands.spawn((
84        Name::new("Instructions"),
85        Text::new(
86            "Mouse up or down: pitch\n\
87            Mouse left or right: yaw\n\
88            Mouse buttons: roll",
89        ),
90        Node {
91            position_type: PositionType::Absolute,
92            top: px(12),
93            left: px(12),
94            ..default()
95        },
96    ));
97}
98
99fn orbit(
100    mut camera: Single<&mut Transform, With<Camera>>,
101    camera_settings: Res<CameraSettings>,
102    mouse_buttons: Res<ButtonInput<MouseButton>>,
103    mouse_motion: Res<AccumulatedMouseMotion>,
104    time: Res<Time>,
105) {
106    let delta = mouse_motion.delta;
107    let mut delta_roll = 0.0;
108
109    if mouse_buttons.pressed(MouseButton::Left) {
110        delta_roll -= 1.0;
111    }
112    if mouse_buttons.pressed(MouseButton::Right) {
113        delta_roll += 1.0;
114    }
115
116    // Mouse motion is one of the few inputs that should not be multiplied by delta time,
117    // as we are already receiving the full movement since the last frame was rendered. Multiplying
118    // by delta time here would make the movement slower that it should be.
119    let delta_pitch = delta.y * camera_settings.pitch_speed;
120    let delta_yaw = delta.x * camera_settings.yaw_speed;
121
122    // Conversely, we DO need to factor in delta time for mouse button inputs.
123    delta_roll *= camera_settings.roll_speed * time.delta_secs();
124
125    // Obtain the existing pitch, yaw, and roll values from the transform.
126    let (yaw, pitch, roll) = camera.rotation.to_euler(EulerRot::YXZ);
127
128    // Establish the new yaw and pitch, preventing the pitch value from exceeding our limits.
129    let pitch = (pitch + delta_pitch).clamp(
130        camera_settings.pitch_range.start,
131        camera_settings.pitch_range.end,
132    );
133    let roll = roll + delta_roll;
134    let yaw = yaw + delta_yaw;
135    camera.rotation = Quat::from_euler(EulerRot::YXZ, yaw, pitch, roll);
136
137    // Adjust the translation to maintain the correct orientation toward the orbit target.
138    // In our example it's a static target, but this could easily be customized.
139    let target = Vec3::ZERO;
140    camera.translation = target - camera.forward() * camera_settings.orbit_distance;
141}
camera_orbit/camera_orbit.rs

camera_orbit/
camera_orbit.rs
