implementing orbit behavior between 2D circles

[hblzr]

Hi,

Does the bevy engine already have a plugin that would make it easier to set one 2D Circle to orbit around another 2D Circle (or just x, z)?

If we don't have a plugin for that yet what would be the closest code sample (from bevy's examples) that I could use as base start?

[bugsweeper]

I think the most close to orbit is moving sprite example but instead of just move up and down, you should use something like polar coordinate system

//! Renders a 2D scene containing a single, moving sprite.

use bevy::prelude::*;
use std::f32::consts::PI;

const ORBIT_CENTER: Vec3 = Vec3 {
    x: 100.0,
    y: 0.0,
    z: 0.0,
};

const ORBIT_RADIUS: f32 = 150.0;

// Negative is clockwise
// Positive is counterclockwise
// Currently half a turn per second counterclockwise
const ORBIT_SPEED: f32 = 0.5;

fn orbit_pos(mut angle: f32) -> Vec3 {
    angle *= ORBIT_SPEED;
    ORBIT_RADIUS * Vec3::new(angle.cos(), angle.sin(), 0.0)
}

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

fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
    commands.spawn(Camera2dBundle::default());
    commands.spawn((SpriteBundle {
        texture: asset_server.load("branding/icon.png"),
        transform: Transform::from_translation(ORBIT_CENTER + orbit_pos(0.0)),
        ..default()
    },));
}

/// The sprite is animated by changing its translation depending on the time that has passed since
/// startup.
fn sprite_movement(time: Res<Time>, mut sprite_position: Query<&mut Transform, Without<Camera>>) {
    for mut transform in &mut sprite_position {
        transform.translation = ORBIT_CENTER + orbit_pos(time.elapsed_seconds() * 2.0 * PI)
    }
}