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
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
//! Demonstrates depth of field (DOF).
//!
//! The depth of field effect simulates the blur that a real camera produces on
//! objects that are out of focus.
//!
//! The test scene is inspired by [a blog post on depth of field in Unity].
//! However, the technique used in Bevy has little to do with that blog post,
//! and all the assets are original.
//!
//! [a blog post on depth of field in Unity]: https://catlikecoding.com/unity/tutorials/advanced-rendering/depth-of-field/

use bevy::{
    core_pipeline::{
        bloom::BloomSettings,
        dof::{self, DepthOfFieldMode, DepthOfFieldSettings},
        tonemapping::Tonemapping,
    },
    pbr::Lightmap,
    prelude::*,
    render::camera::PhysicalCameraParameters,
};

/// The increments in which the user can adjust the focal distance, in meters
/// per frame.
const FOCAL_DISTANCE_SPEED: f32 = 0.05;
/// The increments in which the user can adjust the f-number, in units per frame.
const APERTURE_F_STOP_SPEED: f32 = 0.01;

/// The minimum distance that we allow the user to focus on.
const MIN_FOCAL_DISTANCE: f32 = 0.01;
/// The minimum f-number that we allow the user to set.
const MIN_APERTURE_F_STOPS: f32 = 0.05;

/// A resource that stores the settings that the user can change.
#[derive(Clone, Copy, Resource)]
struct AppSettings {
    /// The distance from the camera to the area in the most focus.
    focal_distance: f32,

    /// The [f-number]. Lower numbers cause objects outside the focal distance
    /// to be blurred more.
    ///
    /// [f-number]: https://en.wikipedia.org/wiki/F-number
    aperture_f_stops: f32,

    /// Whether depth of field is on, and, if so, whether we're in Gaussian or
    /// bokeh mode.
    mode: Option<DepthOfFieldMode>,
}

fn main() {
    App::new()
        .init_resource::<AppSettings>()
        .add_plugins(DefaultPlugins.set(WindowPlugin {
            primary_window: Some(Window {
                title: "Bevy Depth of Field Example".to_string(),
                ..default()
            }),
            ..default()
        }))
        .add_systems(Startup, setup)
        .add_systems(Update, tweak_scene)
        .add_systems(
            Update,
            (adjust_focus, change_mode, update_dof_settings, update_text).chain(),
        )
        .run();
}

fn setup(mut commands: Commands, asset_server: Res<AssetServer>, app_settings: Res<AppSettings>) {
    // Spawn the camera. Enable HDR and bloom, as that highlights the depth of
    // field effect.
    let mut camera = commands.spawn(Camera3dBundle {
        transform: Transform::from_xyz(0.0, 4.5, 8.25).looking_at(Vec3::ZERO, Vec3::Y),
        camera: Camera {
            hdr: true,
            ..default()
        },
        tonemapping: Tonemapping::TonyMcMapface,
        ..default()
    });
    camera.insert(BloomSettings::NATURAL);

    // Insert the depth of field settings.
    if let Some(dof_settings) = Option::<DepthOfFieldSettings>::from(*app_settings) {
        camera.insert(dof_settings);
    }

    // Spawn the scene.
    commands.spawn(SceneBundle {
        scene: asset_server.load(
            GltfAssetLabel::Scene(0)
                .from_asset("models/DepthOfFieldExample/DepthOfFieldExample.glb"),
        ),
        ..default()
    });

    // Spawn the help text.
    commands.spawn(
        TextBundle {
            text: create_text(&app_settings),
            ..default()
        }
        .with_style(Style {
            position_type: PositionType::Absolute,
            bottom: Val::Px(12.0),
            left: Val::Px(12.0),
            ..default()
        }),
    );
}

/// Adjusts the focal distance and f-number per user inputs.
fn adjust_focus(input: Res<ButtonInput<KeyCode>>, mut app_settings: ResMut<AppSettings>) {
    // Change the focal distance if the user requested.
    let distance_delta = if input.pressed(KeyCode::ArrowDown) {
        -FOCAL_DISTANCE_SPEED
    } else if input.pressed(KeyCode::ArrowUp) {
        FOCAL_DISTANCE_SPEED
    } else {
        0.0
    };

    // Change the f-number if the user requested.
    let f_stop_delta = if input.pressed(KeyCode::ArrowLeft) {
        -APERTURE_F_STOP_SPEED
    } else if input.pressed(KeyCode::ArrowRight) {
        APERTURE_F_STOP_SPEED
    } else {
        0.0
    };

    app_settings.focal_distance =
        (app_settings.focal_distance + distance_delta).max(MIN_FOCAL_DISTANCE);
    app_settings.aperture_f_stops =
        (app_settings.aperture_f_stops + f_stop_delta).max(MIN_APERTURE_F_STOPS);
}

/// Changes the depth of field mode (Gaussian, bokeh, off) per user inputs.
fn change_mode(input: Res<ButtonInput<KeyCode>>, mut app_settings: ResMut<AppSettings>) {
    if !input.just_pressed(KeyCode::Space) {
        return;
    }

    app_settings.mode = match app_settings.mode {
        Some(DepthOfFieldMode::Bokeh) => Some(DepthOfFieldMode::Gaussian),
        Some(DepthOfFieldMode::Gaussian) => None,
        None => Some(DepthOfFieldMode::Bokeh),
    }
}

impl Default for AppSettings {
    fn default() -> Self {
        Self {
            // Objects 7 meters away will be in full focus.
            focal_distance: 7.0,

            // Set a nice blur level.
            //
            // This is a really low F-number, but we want to demonstrate the
            // effect, even if it's kind of unrealistic.
            aperture_f_stops: 1.0 / 8.0,

            // Turn on bokeh by default, as it's the nicest-looking technique.
            mode: Some(DepthOfFieldMode::Bokeh),
        }
    }
}

/// Writes the depth of field settings into the camera.
fn update_dof_settings(
    mut commands: Commands,
    view_targets: Query<Entity, With<Camera>>,
    app_settings: Res<AppSettings>,
) {
    let dof_settings: Option<DepthOfFieldSettings> = (*app_settings).into();
    for view in view_targets.iter() {
        match dof_settings {
            None => {
                commands.entity(view).remove::<DepthOfFieldSettings>();
            }
            Some(dof_settings) => {
                commands.entity(view).insert(dof_settings);
            }
        }
    }
}

/// Makes one-time adjustments to the scene that can't be encoded in glTF.
fn tweak_scene(
    mut commands: Commands,
    asset_server: Res<AssetServer>,
    mut materials: ResMut<Assets<StandardMaterial>>,
    mut lights: Query<&mut DirectionalLight, Changed<DirectionalLight>>,
    mut named_entities: Query<
        (Entity, &Name, &Handle<StandardMaterial>),
        (With<Handle<Mesh>>, Without<Lightmap>),
    >,
) {
    // Turn on shadows.
    for mut light in lights.iter_mut() {
        light.shadows_enabled = true;
    }

    // Add a nice lightmap to the circuit board.
    for (entity, name, material) in named_entities.iter_mut() {
        if &**name == "CircuitBoard" {
            materials.get_mut(material).unwrap().lightmap_exposure = 10000.0;
            commands.entity(entity).insert(Lightmap {
                image: asset_server.load("models/DepthOfFieldExample/CircuitBoardLightmap.hdr"),
                ..default()
            });
        }
    }
}

/// Update the help text entity per the current app settings.
fn update_text(mut texts: Query<&mut Text>, app_settings: Res<AppSettings>) {
    for mut text in texts.iter_mut() {
        *text = create_text(&app_settings);
    }
}

/// Regenerates the app text component per the current app settings.
fn create_text(app_settings: &AppSettings) -> Text {
    Text::from_section(app_settings.help_text(), TextStyle::default())
}

impl From<AppSettings> for Option<DepthOfFieldSettings> {
    fn from(app_settings: AppSettings) -> Self {
        app_settings.mode.map(|mode| DepthOfFieldSettings {
            mode,
            focal_distance: app_settings.focal_distance,
            aperture_f_stops: app_settings.aperture_f_stops,
            max_depth: 14.0,
            ..default()
        })
    }
}

impl AppSettings {
    /// Builds the help text.
    fn help_text(&self) -> String {
        let Some(mode) = self.mode else {
            return "Mode: Off (Press Space to change)".to_owned();
        };

        // We leave these as their defaults, so we don't need to store them in
        // the app settings and can just fetch them from the default camera
        // parameters.
        let sensor_height = PhysicalCameraParameters::default().sensor_height;
        let fov = PerspectiveProjection::default().fov;

        format!(
            "Focal distance: {} m (Press Up/Down to change)
Aperture F-stops: f/{} (Press Left/Right to change)
Sensor height: {}mm
Focal length: {}mm
Mode: {} (Press Space to change)",
            self.focal_distance,
            self.aperture_f_stops,
            sensor_height * 1000.0,
            dof::calculate_focal_length(sensor_height, fov) * 1000.0,
            match mode {
                DepthOfFieldMode::Bokeh => "Bokeh",
                DepthOfFieldMode::Gaussian => "Gaussian",
            }
        )
    }
}