1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
//! This example showcases auto exposure,
//! which automatically (but not instantly) adjusts the brightness of the scene in a way that mimics the function of the human eye.
//! Auto exposure requires compute shader capabilities, so it's not available on WebGL.
//!
//! ## Controls
//!
//! | Key Binding        | Action                                 |
//! |:-------------------|:---------------------------------------|
//! | `Left` / `Right`   | Rotate Camera                          |
//! | `C`                | Toggle Compensation Curve              |
//! | `M`                | Toggle Metering Mask                   |
//! | `V`                | Visualize Metering Mask                |

use bevy::{
    core_pipeline::{
        auto_exposure::{AutoExposureCompensationCurve, AutoExposurePlugin, AutoExposureSettings},
        Skybox,
    },
    math::{cubic_splines::LinearSpline, primitives::Plane3d, vec2},
    prelude::*,
};

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_plugins(AutoExposurePlugin)
        .add_systems(Startup, setup)
        .add_systems(Update, example_control_system)
        .run();
}

fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
    mut compensation_curves: ResMut<Assets<AutoExposureCompensationCurve>>,
    asset_server: Res<AssetServer>,
) {
    let metering_mask = asset_server.load("textures/basic_metering_mask.png");

    commands.spawn((
        Camera3dBundle {
            camera: Camera {
                hdr: true,
                ..default()
            },
            transform: Transform::from_xyz(1.0, 0.0, 0.0).looking_at(Vec3::ZERO, Vec3::Y),
            ..default()
        },
        AutoExposureSettings {
            metering_mask: metering_mask.clone(),
            ..default()
        },
        Skybox {
            image: asset_server.load("environment_maps/pisa_specular_rgb9e5_zstd.ktx2"),
            brightness: bevy::pbr::light_consts::lux::DIRECT_SUNLIGHT,
        },
    ));

    commands.insert_resource(ExampleResources {
        basic_compensation_curve: compensation_curves.add(
            AutoExposureCompensationCurve::from_curve(LinearSpline::new([
                vec2(-4.0, -2.0),
                vec2(0.0, 0.0),
                vec2(2.0, 0.0),
                vec2(4.0, 2.0),
            ]))
            .unwrap(),
        ),
        basic_metering_mask: metering_mask.clone(),
    });

    let plane = meshes.add(Mesh::from(
        Plane3d {
            normal: -Dir3::Z,
            half_size: Vec2::new(2.0, 0.5),
        }
        .mesh(),
    ));

    // Build a dimly lit box around the camera, with a slot to see the bright skybox.
    for level in -1..=1 {
        for side in [-Vec3::X, Vec3::X, -Vec3::Z, Vec3::Z] {
            if level == 0 && Vec3::Z == side {
                continue;
            }

            let height = Vec3::Y * level as f32;

            commands.spawn(PbrBundle {
                mesh: plane.clone(),
                material: materials.add(StandardMaterial {
                    base_color: Color::srgb(
                        0.5 + side.x * 0.5,
                        0.75 - level as f32 * 0.25,
                        0.5 + side.z * 0.5,
                    ),
                    ..default()
                }),
                transform: Transform::from_translation(side * 2.0 + height)
                    .looking_at(height, Vec3::Y),
                ..default()
            });
        }
    }

    commands.insert_resource(AmbientLight {
        color: Color::WHITE,
        brightness: 0.0,
    });

    commands.spawn(PointLightBundle {
        point_light: PointLight {
            intensity: 2000.0,
            ..default()
        },
        transform: Transform::from_xyz(0.0, 0.0, 0.0),
        ..default()
    });

    commands.spawn(ImageBundle {
        image: UiImage {
            texture: metering_mask,
            ..default()
        },
        style: Style {
            width: Val::Percent(100.0),
            height: Val::Percent(100.0),
            ..default()
        },
        ..default()
    });

    let text_style = TextStyle::default();

    commands.spawn(
        TextBundle::from_section(
            "Left / Right - Rotate Camera\nC - Toggle Compensation Curve\nM - Toggle Metering Mask\nV - Visualize Metering Mask",
            text_style.clone(),
        )
        .with_style(Style {
            position_type: PositionType::Absolute,
            top: Val::Px(12.0),
            left: Val::Px(12.0),
            ..default()
        }),
    );

    commands.spawn((
        TextBundle::from_section("", text_style).with_style(Style {
            position_type: PositionType::Absolute,
            top: Val::Px(10.0),
            right: Val::Px(10.0),
            ..default()
        }),
        ExampleDisplay,
    ));
}

#[derive(Component)]
struct ExampleDisplay;

#[derive(Resource)]
struct ExampleResources {
    basic_compensation_curve: Handle<AutoExposureCompensationCurve>,
    basic_metering_mask: Handle<Image>,
}

fn example_control_system(
    mut camera: Query<(&mut Transform, &mut AutoExposureSettings), With<Camera3d>>,
    mut display: Query<&mut Text, With<ExampleDisplay>>,
    mut mask_image: Query<&mut Style, With<UiImage>>,
    time: Res<Time>,
    input: Res<ButtonInput<KeyCode>>,
    resources: Res<ExampleResources>,
) {
    let (mut camera_transform, mut auto_exposure) = camera.single_mut();

    let rotation = if input.pressed(KeyCode::ArrowLeft) {
        time.delta_seconds()
    } else if input.pressed(KeyCode::ArrowRight) {
        -time.delta_seconds()
    } else {
        0.0
    };

    camera_transform.rotate_around(Vec3::ZERO, Quat::from_rotation_y(rotation));

    if input.just_pressed(KeyCode::KeyC) {
        auto_exposure.compensation_curve =
            if auto_exposure.compensation_curve == resources.basic_compensation_curve {
                Handle::default()
            } else {
                resources.basic_compensation_curve.clone()
            };
    }

    if input.just_pressed(KeyCode::KeyM) {
        auto_exposure.metering_mask =
            if auto_exposure.metering_mask == resources.basic_metering_mask {
                Handle::default()
            } else {
                resources.basic_metering_mask.clone()
            };
    }

    mask_image.single_mut().display = if input.pressed(KeyCode::KeyV) {
        Display::Flex
    } else {
        Display::None
    };

    let mut display = display.single_mut();
    display.sections[0].value = format!(
        "Compensation Curve: {}\nMetering Mask: {}",
        if auto_exposure.compensation_curve == resources.basic_compensation_curve {
            "Enabled"
        } else {
            "Disabled"
        },
        if auto_exposure.metering_mask == resources.basic_metering_mask {
            "Enabled"
        } else {
            "Disabled"
        },
    );
}