world_to_viewport works incorrectly? and a few other questions about the coordinate system

[Gor-Madatyan]

Questions

Which coordinate systems does Bevy use? and what are their descriptions

As far as I know, those are world,viewport,local(for children of some entity) coordinate systems.

And are the local coordinates applicable only to the children of the camera? Or Not?

how to get world | viewport coordinates from local coordinates?

🔢

Main Question

(tested in 0.10, 0.11)

For some reason, world_to_viewport, viewport_to_world_2d and others calculates coordinates relative to top-right corner of the screen world_to_viewport points to the upper right corner when converting [0.0, 0.0], but was supposed to show the upper left corner according to this

some info about the system:

AdapterInfo { name: "GeForce RTX 2060", vendor: 4318, device: 7957, device_type: DiscreteGpu, driver: "NVIDIA", driver_info: "451.67", backend: Vulkan }
SystemInfo { os: "Windows 11 Home", kernel: "22621", cpu: "Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz", core_count: "6", memory: "15.8 GiB" }

Code which confirms my words

use bevy::prelude::*;

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


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


fn get_space_center(mut commands:Commands,asset_server:Res<AssetServer>, query: Query<(&Camera,&GlobalTransform)>) {
    let camera = query.get_single().unwrap();
    let cords=camera.0.world_to_viewport(camera.1, Vec3::new(0.0,0.0,0.0)).unwrap();
commands.spawn(SpriteBundle {
        texture: asset_server.load("planet00.png"),
        transform:Transform::from_translation(Vec3::new(cords.x,cords.y,0.0)),
        ..Default::default()
    });
    dbg!(cords);
}

[superdump]

Right-handed, x-right, y-up, z-back and cameras look along -z.

[tim-blackbird]

Methods like world_to_viewport convert between 'viewport space' and 'world space'; they don't convert a world space position to another world space position that is relative to the viewport.
world_to_viewport is useful when you want to position a UI element (which are positioned in 'viewport space') relative to something in world space (like a sprite).

If you want to place an image relative to the window you probably want to take a look at the ui examples or ImageBundle specifically.

[Gor-Madatyan]

Thank you, it explains all