bevy/examples/3d/3d_gizmos.rs

//! This example demonstrates Bevy's immediate mode drawing API intended for visual debugging.

use std::f32::consts::PI;

use bevy::prelude::*;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup)
        .add_systems(Update, (system, rotate_camera, update_config))
        .run();
}

fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    commands.spawn(Camera3dBundle {
        transform: Transform::from_xyz(0., 1.5, 6.).looking_at(Vec3::ZERO, Vec3::Y),
        ..default()
    });
    // plane
    commands.spawn(PbrBundle {
        mesh: meshes.add(shape::Plane::from_size(5.0)),
        material: materials.add(Color::rgb(0.3, 0.5, 0.3)),
        ..default()
    });
    // cube
    commands.spawn(PbrBundle {
        mesh: meshes.add(shape::Cube { size: 1.0 }),
        material: materials.add(Color::rgb(0.8, 0.7, 0.6)),
        transform: Transform::from_xyz(0.0, 0.5, 0.0),
        ..default()
    });
    // light
    commands.spawn(PointLightBundle {
        point_light: PointLight {
            intensity: 250000.0,
            shadows_enabled: true,
            ..default()
        },
        transform: Transform::from_xyz(4.0, 8.0, 4.0),
        ..default()
    });

    // example instructions
    commands.spawn(
        TextBundle::from_section(
            "Press 'D' to toggle drawing gizmos on top of everything else in the scene\n\
            Press 'P' to toggle perspective for line gizmos\n\
            Hold 'Left' or 'Right' to change the line width",
            TextStyle {
                font_size: 20.,
                ..default()
            },
        )
        .with_style(Style {
            position_type: PositionType::Absolute,
            top: Val::Px(12.0),
            left: Val::Px(12.0),
            ..default()
        }),
    );
}

fn system(mut gizmos: Gizmos, time: Res<Time>) {
    gizmos.cuboid(
        Transform::from_translation(Vec3::Y * 0.5).with_scale(Vec3::splat(1.)),
        Color::BLACK,
    );
    gizmos.rect(
        Vec3::new(time.elapsed_seconds().cos() * 2.5, 1., 0.),
        Quat::from_rotation_y(PI / 2.),
        Vec2::splat(2.),
        Color::GREEN,
    );

    gizmos.sphere(Vec3::new(1., 0.5, 0.), Quat::IDENTITY, 0.5, Color::RED);

    for y in [0., 0.5, 1.] {
        gizmos.ray(
            Vec3::new(1., y, 0.),
            Vec3::new(-3., (time.elapsed_seconds() * 3.).sin(), 0.),
            Color::BLUE,
        );
    }

    // Circles have 32 line-segments by default.
    gizmos.circle(Vec3::ZERO, Vec3::Y, 3., Color::BLACK);
    // You may want to increase this for larger circles or spheres.
    gizmos
        .circle(Vec3::ZERO, Vec3::Y, 3.1, Color::NAVY)
        .segments(64);
    gizmos
        .sphere(Vec3::ZERO, Quat::IDENTITY, 3.2, Color::BLACK)
        .circle_segments(64);

    gizmos.arrow(Vec3::ZERO, Vec3::ONE * 1.5, Color::YELLOW);
}

fn rotate_camera(mut query: Query<&mut Transform, With<Camera>>, time: Res<Time>) {
    let mut transform = query.single_mut();

    transform.rotate_around(Vec3::ZERO, Quat::from_rotation_y(time.delta_seconds() / 2.));
}

fn update_config(
    mut config: ResMut<GizmoConfig>,
    keyboard: Res<ButtonInput<KeyCode>>,
    time: Res<Time>,
) {
    if keyboard.just_pressed(KeyCode::KeyD) {
        config.depth_bias = if config.depth_bias == 0. { -1. } else { 0. };
    }
    if keyboard.just_pressed(KeyCode::KeyP) {
        // Toggle line_perspective
        config.line_perspective ^= true;
        // Increase the line width when line_perspective is on
        config.line_width *= if config.line_perspective { 5. } else { 1. / 5. };
    }

    if keyboard.pressed(KeyCode::ArrowRight) {
        config.line_width += 5. * time.delta_seconds();
    }
    if keyboard.pressed(KeyCode::ArrowLeft) {
        config.line_width -= 5. * time.delta_seconds();
    }
}