wsg/lib/examples/cube.rs

//! Step 5 — MVP 3D: a lit unit cube that rotates; **Step 10** — the cube is **textured**
//! (procedural checkerboard) via the new diffuse path (bind group `@group(2)`).
//!
//! Demonstrates the MVP goal of ROADMAP 1.3 + 1.5: a 3D mesh with Phong lighting on screen.
//! Follows the declarative workflow (like `simple`): `AppBuilder` + automatic scene, **no wgpu import**.
//! Since Step 7 the scene owns its `PipelineCache`: go through `register_shader` +
//! `add_material_shader`/`add_material_texture` + `create_mesh` + `add_entity`. Since Step 8 the mesh
//! is declared from a **`Geometry`** (positions, normals, indices). Since Step 10 (D4) a texture is
//! registered by id (`add_texture`) and a textured material bound to it (`add_material_texture`);
//! the texture is generated *procedurally* (RGBA 8×8 checkerboard) to stay self-contained, no on-disk asset.
//! The default active camera (`Scene::default`, position (0,0,3), fov 45°) frames the cube, and
//! `AppHandler::update` rotates the entity via `set_entity_transform` each frame.
use glam::{Quat, Vec3};
use wsg_lib::AppHandler;
use wsg_lib::app::AppBuilder;
use wsg_lib::math::cube;
use wsg_lib::resources::Texture;
use wsg_lib::utils::WsgError;

/// Demo handler: rotates the textured cube in `update`.
struct Cube {
    /// Cumulative rotation angle (radians), incremented each frame.
    angle: f32,
}

/// Generates a *procedural* RGBA 8×8 checkerboard (white/brick), no on-disk asset, to texture the
/// cube (Step 10, D3/D4). Returned as a raw RGBA8 `Vec<u8>`, loadable via `Texture::from_rgba8`.
fn checkerboard_rgba() -> Vec<u8> {
    const SIZE: u32 = 8;
    let mut rgba = Vec::with_capacity((SIZE * SIZE * 4) as usize);
    for y in 0..SIZE {
        for x in 0..SIZE {
            let even = (x + y) % 2 == 0;
            let (r, g, b) = if even { (255, 255, 255) } else { (190, 40, 40) };
            rgba.extend_from_slice(&[r, g, b, 255]);
        }
    }
    rgba
}

impl AppHandler for Cube {
    fn setup(&mut self, app: &mut wsg_lib::App) {
        // Phong shader `standard` (carries the frame + object + texture bind groups, Step 10).
        app.scene
            .register_shader("standard", wsg_lib::utils::STANDARD_SHADER_PATH)
            .unwrap();

        // Builds the checkerboard texture with the Context's device/queue (via `app.context()`), then
        // registers it in the scene by id; a textured material is then bound to that id.
        let (device, queue) = {
            let ctx = app.context();
            (ctx.device.clone(), ctx.queue.clone())
        };
        let texture =
            Texture::from_rgba8(&device, &queue, 8, 8, &checkerboard_rgba(), "checker").unwrap();
        app.scene.add_texture("checker_texture", texture).unwrap();
        app.scene
            .add_material_texture("cube_material", "standard", "checker_texture")
            .unwrap();

        app.scene
            .create_mesh("cube_mesh", cube(1.0), Some("cube_material"))
            .unwrap();
        app.scene.add_entity("cube", "cube_mesh").unwrap();

        // Step 12 (Phase 4.2): in addition to the default directional light (+Z), a warm **point** light
        // is added in front of the cube. Its halo (linear attenuation over the
        // radius) is visible on the near face of the cube, on top of the directional lighting.
        app.scene
            .add_point_light(
                Vec3::new(1.0, 0.5, 1.5), // world position, in front/right of the cube
                [1.0, 0.7, 0.3],          // warm tint
                1.0,                      // intensity
                3.0,                      // attenuation radius
            )
            .unwrap();

        // Step 13 (Phase 4.2): a green **spot** light aimed at the cube from the left.
        // The cone (half-angle ~20°) projects a directed beam onto the cube's faces, with a
        // smoothed penumbra at the edge and linear attenuation over the radius.
        app.scene
            .add_spot_light(
                Vec3::new(-2.0, 1.0, 1.5), // world position, left/above/behind the camera
                Vec3::new(2.0, -1.0, -1.5).normalize(), // cone axis, toward the cube (origin)
                [0.3, 1.0, 0.4],           // green tint
                1.2,                       // intensity
                4.0,                       // attenuation radius
                0.35,                      // half-angle (~20°) in radians
            )
            .unwrap();
    }

    fn update(&mut self, app: &mut wsg_lib::App) {
        // Cumulative cube rotation (double axis for a more readable motion).
        self.angle += 0.02;
        let base = *app
            .scene
            .entity_transform("cube")
            .expect("cube entity present");
        let mut transform = base;
        transform.rotation =
            Quat::from_rotation_y(self.angle) * Quat::from_rotation_x(self.angle * 0.3);
        app.scene.set_entity_transform("cube", transform);
    }
}

#[pollster::main]
async fn main() -> Result<(), WsgError> {
    let app = AppBuilder::new().title("WSG Cube").build().await?;
    app.run(Cube { angle: 0.0 })
}