hello_cube/
hello_cube.rs

1//! # Hello Cube
2//!
3//! The simplest possible Vertra scene: a single orange cube that slowly
4//! rotates in place.  This example shows the minimum boilerplate required
5//! to open a window and render geometry.
6//!
7//! **Run:**
8//! ```sh
9//! cargo run --example hello_cube
10//! ```
11//!
12//! **Controls:** close the window to exit.
13
14use vertra::camera::Camera;
15use vertra::geometry::Geometry;
16use vertra::objects::Object;
17use vertra::transform::Transform;
18use vertra::window::Window;
19
20/// Application state — we cache the numeric ID resolved during startup so that
21/// `on_update` never pays the cost of a string-hash lookup every frame.
22struct AppState {
23    cube_id: Option<usize>,
24}
25
26fn main() {
27    Window::new(AppState { cube_id: None })
28        .with_title("Hello, Cube!")
29        .with_camera(
30            Camera::new()
31                .with_position([0.0, 2.0, -5.0])
32                .with_rotation(90.0, -15.0),
33        )
34        .on_startup(|state, scene, _| {
35            // Spawn a single cube at the world origin.
36            let id = scene.spawn(
37                Object {
38                    name: "Cube".to_string(),
39                    str_id: "cube".to_string(),
40                    geometry: Some(Geometry::Cube { size: 1.5 }),
41                    color: [0.9, 0.5, 0.2, 1.0], // warm orange
42                    transform: Transform::default(),
43                    ..Default::default()
44                },
45                None, // no parent — this is a root object
46            );
47            // Cache the ID so on_update can find it cheaply.
48            state.cube_id = Some(id);
49        })
50        .on_update(|state, scene, ctx| {
51            // Rotate 45° per second around the Y-axis.
52            if let Some(cube) = state.cube_id.and_then(|id| scene.world.get_mut(id)) {
53                cube.transform.rotation[1] += 45.0 * ctx.dt;
54            }
55        })
56        .create();
57}
58
hello_cube/hello_cube.rs

hello_cube/
hello_cube.rs
