# Orthographic View

The default [Camera3dBundle](https://docs.rs/bevy/latest/bevy/core_pipeline/core_3d/struct.Camera3dBundle.html) has a property that objects near the camera are larger and objects far away from the camera are smaller.

![Orthographic View 1](./pic/orthographic_view_1.png)

This may not be wanted for some engineering problems, which require objects with the same size look the same no matter the distances between them and the camera.

![Orthographic View 2](./pic/orthographic_view_2.png)

This can be done by modifying the [projection](https://docs.rs/bevy/latest/bevy/core_pipeline/core_3d/struct.Camera3dBundle.html#structfield.projection) of [Camera3dBundle](https://docs.rs/bevy/latest/bevy/core_pipeline/core_3d/struct.Camera3dBundle.html).

```rust
commands.spawn(Camera3dBundle {
    transform: Transform::from_xyz(2., 1., 3.).looking_at(Vec3::ZERO, Vec3::Y),
    projection: Projection::Orthographic(OrthographicProjection {
        scaling_mode: ScalingMode::WindowSize(200.),
        ..default()
    }),
    ..default()
});
```

We set the [projection](https://docs.rs/bevy/latest/bevy/core_pipeline/core_3d/struct.Camera3dBundle.html#structfield.projection) to [Projection::Orthographic](https://docs.rs/bevy/latest/bevy/render/camera/enum.Projection.html#variant.Orthographic) and pass an [OrthographicProjection](https://docs.rs/bevy/latest/bevy/render/camera/struct.OrthographicProjection.html) to it.
In the [OrthographicProjection](https://docs.rs/bevy/latest/bevy/render/camera/struct.OrthographicProjection.html), we set the [scaling_mode](https://docs.rs/bevy/latest/bevy/render/camera/struct.OrthographicProjection.html#structfield.scaling_mode) to specify the size of one unit on the screen.
In our case, we specify `ScalingMode::WindowSize(200.)`, which maps one unit in the 3D space to 200 units (usually pixels) in the window.

The full code is as follows:

```rust
use bevy::{
    app::{App, Startup},
    asset::Assets,
    core_pipeline::core_3d::Camera3dBundle,
    ecs::system::{Commands, ResMut},
    math::Vec3,
    pbr::{PbrBundle, PointLightBundle, StandardMaterial},
    render::{camera::{OrthographicProjection, Projection, ScalingMode}, mesh::{shape::Cube, Mesh}},
    transform::components::Transform,
    utils::default,
    DefaultPlugins,
};

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

fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    commands.spawn(Camera3dBundle {
        transform: Transform::from_xyz(2., 1., 3.).looking_at(Vec3::ZERO, Vec3::Y),
        projection: Projection::Orthographic(OrthographicProjection {
            scaling_mode: ScalingMode::WindowSize(200.),
            ..default()
        }),
        ..default()
    });

    commands.spawn(PbrBundle {
        mesh: meshes.add(Cube::new(1.).into()).into(),
        material: materials.add(StandardMaterial::default()).into(),
        ..default()
    });

    commands.spawn(PointLightBundle {
        transform: Transform::from_xyz(2., 2., 1.),
        ..default()
    });
}
```

The result is shown by the second picture above.

If we use the default [ScalingMode](https://docs.rs/bevy/latest/bevy/render/camera/enum.ScalingMode.html), the scene will be very small, since one unit in the 3D space maps to 1 unit in the window.

![Orthographic View 3](./pic/orthographic_view_3.png)

The cube becomes a small white point at the center of the window.

:arrow_right:  Next: [Cube](./cube.md)

:blue_book: Back: [Table of contents](./../README.md)