camera_positions_and_directions.md

Camera Positions And Directions

We can change camera positions and directions.

This is done by the transform in Camera3dBundle.

commands.spawn(Camera3dBundle {
    transform: Transform::from_xyz(2., 1., 3.).looking_at(Vec3::ZERO, Vec3::Y),
    ..default()
});

To change the camera position, we use the function from_xyz of Transform. This function sets the position of the camera. In the example, we sets the position of our camera to (2, 1, 3). To change the camera direction, we use the method looking_at of Transform. The method takes two parameters: target and up. The camera will sit at the position specified by from_xyz and look at the target, which is another position. The parameter up is a direction pointing to the sky of the camera. In the example, our camera looks at the origin, and the sky is on top of the camera. Note that Vec3::Y means the direction (0, 1, 0).

The full code is as follows:

use bevy::{
    app::{App, Startup},
    asset::Assets,
    core_pipeline::core_3d::Camera3dBundle,
    ecs::system::{Commands, ResMut},
    math::Vec3,
    pbr::{PbrBundle, PointLightBundle, StandardMaterial},
    render::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),
        ..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()
    });
}

Currently, we omit the explanation of PbrBundle and PointLightBundle. These bundles will be explained later. Basically, we add a cube and a light to the scene. The cube is centered at the origin.

Result:

➡️ Next: Orthographic View

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