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
//! Simple benchmark to test rendering many point lights.
//! Run with `WGPU_SETTINGS_PRIO=webgl2` to restrict to uniform buffers and max 256 lights.

use std::f64::consts::PI;

use bevy::{
    color::palettes::css::DEEP_PINK,
    diagnostic::{FrameTimeDiagnosticsPlugin, LogDiagnosticsPlugin},
    math::{DVec2, DVec3},
    pbr::{ExtractedPointLight, GlobalClusterableObjectMeta},
    prelude::*,
    render::{camera::ScalingMode, Render, RenderApp, RenderSet},
    window::{PresentMode, WindowResolution},
    winit::{UpdateMode, WinitSettings},
};
use rand::{thread_rng, Rng};

fn main() {
    App::new()
        .add_plugins((
            DefaultPlugins.set(WindowPlugin {
                primary_window: Some(Window {
                    resolution: WindowResolution::new(1920.0, 1080.0)
                        .with_scale_factor_override(1.0),
                    title: "many_lights".into(),
                    present_mode: PresentMode::AutoNoVsync,
                    ..default()
                }),
                ..default()
            }),
            FrameTimeDiagnosticsPlugin,
            LogDiagnosticsPlugin::default(),
            LogVisibleLights,
        ))
        .insert_resource(WinitSettings {
            focused_mode: UpdateMode::Continuous,
            unfocused_mode: UpdateMode::Continuous,
        })
        .add_systems(Startup, setup)
        .add_systems(Update, (move_camera, print_light_count))
        .run();
}

fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    warn!(include_str!("warning_string.txt"));

    const LIGHT_RADIUS: f32 = 0.3;
    const LIGHT_INTENSITY: f32 = 1000.0;
    const RADIUS: f32 = 50.0;
    const N_LIGHTS: usize = 100_000;

    commands.spawn(PbrBundle {
        mesh: meshes.add(Sphere::new(RADIUS).mesh().ico(9).unwrap()),
        material: materials.add(Color::WHITE),
        transform: Transform::from_scale(Vec3::NEG_ONE),
        ..default()
    });

    let mesh = meshes.add(Cuboid::default());
    let material = materials.add(StandardMaterial {
        base_color: DEEP_PINK.into(),
        ..default()
    });

    // NOTE: This pattern is good for testing performance of culling as it provides roughly
    // the same number of visible meshes regardless of the viewing angle.
    // NOTE: f64 is used to avoid precision issues that produce visual artifacts in the distribution
    let golden_ratio = 0.5f64 * (1.0f64 + 5.0f64.sqrt());

    // Spawn N_LIGHTS many lights
    commands.spawn_batch((0..N_LIGHTS).map(move |i| {
        let mut rng = thread_rng();

        let spherical_polar_theta_phi = fibonacci_spiral_on_sphere(golden_ratio, i, N_LIGHTS);
        let unit_sphere_p = spherical_polar_to_cartesian(spherical_polar_theta_phi);

        PointLightBundle {
            point_light: PointLight {
                range: LIGHT_RADIUS,
                intensity: LIGHT_INTENSITY,
                color: Color::hsl(rng.gen_range(0.0..360.0), 1.0, 0.5),
                ..default()
            },
            transform: Transform::from_translation((RADIUS as f64 * unit_sphere_p).as_vec3()),
            ..default()
        }
    }));

    // camera
    match std::env::args().nth(1).as_deref() {
        Some("orthographic") => commands.spawn(Camera3dBundle {
            projection: OrthographicProjection {
                scale: 20.0,
                scaling_mode: ScalingMode::FixedHorizontal(1.0),
                ..default()
            }
            .into(),
            ..default()
        }),
        _ => commands.spawn(Camera3dBundle::default()),
    };

    // add one cube, the only one with strong handles
    // also serves as a reference point during rotation
    commands.spawn(PbrBundle {
        mesh,
        material,
        transform: Transform {
            translation: Vec3::new(0.0, RADIUS, 0.0),
            scale: Vec3::splat(5.0),
            ..default()
        },
        ..default()
    });
}

// NOTE: This epsilon value is apparently optimal for optimizing for the average
// nearest-neighbor distance. See:
// http://extremelearning.com.au/how-to-evenly-distribute-points-on-a-sphere-more-effectively-than-the-canonical-fibonacci-lattice/
// for details.
const EPSILON: f64 = 0.36;
fn fibonacci_spiral_on_sphere(golden_ratio: f64, i: usize, n: usize) -> DVec2 {
    DVec2::new(
        PI * 2. * (i as f64 / golden_ratio),
        (1.0 - 2.0 * (i as f64 + EPSILON) / (n as f64 - 1.0 + 2.0 * EPSILON)).acos(),
    )
}

fn spherical_polar_to_cartesian(p: DVec2) -> DVec3 {
    let (sin_theta, cos_theta) = p.x.sin_cos();
    let (sin_phi, cos_phi) = p.y.sin_cos();
    DVec3::new(cos_theta * sin_phi, sin_theta * sin_phi, cos_phi)
}

// System for rotating the camera
fn move_camera(time: Res<Time>, mut camera_query: Query<&mut Transform, With<Camera>>) {
    let mut camera_transform = camera_query.single_mut();
    let delta = time.delta_seconds() * 0.15;
    camera_transform.rotate_z(delta);
    camera_transform.rotate_x(delta);
}

// System for printing the number of meshes on every tick of the timer
fn print_light_count(time: Res<Time>, mut timer: Local<PrintingTimer>, lights: Query<&PointLight>) {
    timer.0.tick(time.delta());

    if timer.0.just_finished() {
        info!("Lights: {}", lights.iter().len());
    }
}

struct LogVisibleLights;

impl Plugin for LogVisibleLights {
    fn build(&self, app: &mut App) {
        let Some(render_app) = app.get_sub_app_mut(RenderApp) else {
            return;
        };

        render_app.add_systems(Render, print_visible_light_count.in_set(RenderSet::Prepare));
    }
}

// System for printing the number of meshes on every tick of the timer
fn print_visible_light_count(
    time: Res<Time>,
    mut timer: Local<PrintingTimer>,
    visible: Query<&ExtractedPointLight>,
    global_light_meta: Res<GlobalClusterableObjectMeta>,
) {
    timer.0.tick(time.delta());

    if timer.0.just_finished() {
        info!(
            "Visible Lights: {}, Rendered Lights: {}",
            visible.iter().len(),
            global_light_meta.entity_to_index.len()
        );
    }
}

struct PrintingTimer(Timer);

impl Default for PrintingTimer {
    fn default() -> Self {
        Self(Timer::from_seconds(1.0, TimerMode::Repeating))
    }
}