cube.md

Cube

Similar to 2D rendering, we can add shapes into the 3D space. This is also done by spawning a bundle, adding a shape to the mesh asset and adding a material to some material asset. The shapes can be found in bevy::prelude::shape.

In the following example, we add a cube to the 3D scene.

We make the app to spawn a PbrBundle.

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

We add a Cube to the PbrBundle. The Cube is also added to the mesh asset. We use the function new of Cube to initialize the cube. The function takes a parameter size, which defines the size of the cube.

We set our camera position to (2, 1, 3) and make it looking at the origin.

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 StandardMaterial and PointLightBundle. They will be explained later. Basically, we make the cube visible by the camera.

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