generate random points outside the screen bevy

random_outside.rs

use bevy::prelude::*;
use rand::{thread_rng, Rng};

fn main() {
    App::new()
        .insert_resource(ClearColor(Color::srgb(1.0, 0.0, 0.0)))
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup)
        .add_systems(Update, point_out)
        .run();
}

fn setup(mut commands: Commands) {
    commands.spawn(Camera2dBundle::default());
}

fn rand_outside(rect: Rect) -> Vec2 {
    let r = rect.inflate(100.0); // we want to be solidly outside the screen, not just on the edge
    let Vec2 {
        x: width,
        y: height,
    } = r.size();
    let perimeter = 2.0 * (width + height);
    let rnum = rand::thread_rng().gen_range(0.0..perimeter);
    if rnum < width {
        // Bottom edge
        Vec2 {
            x: r.min.x + rnum,
            y: r.min.y,
        }
    } else if rnum < width + height {
        // Right edge
        Vec2 {
            x: r.max.x,
            y: r.min.y + (rnum - width),
        }
    } else if rnum < 2.0 * width + height {
        // Top edge
        Vec2 {
            x: r.max.x - (rnum - width - height),
            y: r.max.y,
        }
    } else {
        // Left edge
        Vec2 {
            x: r.min.x,
            y: r.max.y - (rnum - 2.0 * width - height),
        }
    }
}

fn point_out(
    mut gizmos: Gizmos,
    q_window: Query<&Window>,
    q_camera: Query<(&Camera, &GlobalTransform)>,
) {
    let (camera, camera_transform) = q_camera.single();
    let window = q_window.single();
    let w = window.resolution.width();
    let h = window.resolution.height();
    let bottom_right = camera
        .viewport_to_world_2d(camera_transform, Vec2::new(w, h))
        .unwrap();
    let top_left = camera
        .viewport_to_world_2d(camera_transform, Vec2::new(0., 0.))
        .unwrap();

    let rect = Rect::from_corners(top_left, bottom_right);
    let outside = rand_outside(rect);
    gizmos.line_2d(Vec2::ZERO, outside, Color::WHITE);
}