réorg doc

lib/examples/lights/spot_test.rs

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+//! Test dedicated to **spot lights**.
+//!
+//! In this example, **only** a spot light is on (the default directional light is
+//! removed via `clear_lights()`) and the ambient is deliberately **very low**. The cube therefore
+//! appears nearly black except where the spot's cone reaches it: you clearly see
+//!
+//!   1. a **directed beam** (not an omni halo like the point light),
+//!   2. a **smoothed edge** (penumbra) at the cone's limit,
+//!   3. the lighting that **follows the cube** as it rotates (the cone is fixed in world space).
+//!
+//! Run with: `cargo run -p wsg-lib --example spot_test`
+use glam::{Quat, Vec3};
+use wsg_lib::AppHandler;
+use wsg_lib::app::AppBuilder;
+use wsg_lib::mesh::cube;
+use wsg_lib::utils::WsgError;
+
+/// Test handler: cube rotating slowly on two axes, lit **only** by a spot.
+struct SpotTest {
+    angle_x: f32,
+    angle_y: f32,
+}
+
+impl AppHandler for SpotTest {
+    fn setup(&mut self, app: &mut wsg_lib::App) {
+        app.scene
+            .register_shader("standard", wsg_lib::utils::STANDARD_SHADER_PATH)
+            .unwrap();
+        app.scene.add_material_shader("mat", "standard").unwrap();
+        app.scene
+            .create_mesh("cube_mesh", cube(1.0), Some("mat"))
+            .unwrap();
+        app.scene.add_entity("cube", "cube_mesh").unwrap();
+
+        // Remove the default directional light to isolate the spot.
+        app.scene.clear_lights();
+        // Near-zero ambient: the cube is black outside the beam, the cone stands out.
+        app.scene.set_ambient([0.03, 0.03, 0.03]);
+
+        // The spot is above/behind the camera, aimed at the origin (the cube).
+        // World position (0, 2, 3), cone axis toward (0,0,0).
+        let spot_pos = Vec3::new(0.0, 2.0, 3.0);
+        let spot_dir = (Vec3::ZERO - spot_pos).normalize(); // points at the cube
+        app.scene
+            .add_spot_light(
+                spot_pos,
+                spot_dir,
+                [1.0, 0.9, 0.6], // warm tint
+                2.0,             // intensity
+                10.0,            // attenuation radius (wide, the cube is at ~3.6)
+                0.45,            // half-angle (~26°) — wide enough to cover the cube
+            )
+            .unwrap();
+    }
+
+    fn update(&mut self, app: &mut wsg_lib::App) {
+        // Slow rotation on two axes (X and Y): the cone is fixed in world space,
+        // so a fixed region of the cube stays lit while the cube rotates.
+        // The two axes let you see the beam's effect on the 6 faces without
+        // a favored orientation (a Y rotation alone would leave the +Y/-Y faces fixed).
+        self.angle_x += 0.007;
+        self.angle_y += 0.011;
+        let base = *app
+            .scene
+            .entity_transform("cube")
+            .expect("cube entity present");
+        let mut transform = base;
+        // Y * X composition: the X axis rotates in the frame already oriented by Y,
+        // which gives a precession motion (all vertices pass in front of
+        // the cone in turn).
+        transform.rotation =
+            Quat::from_rotation_y(self.angle_y) * Quat::from_rotation_x(self.angle_x);
+        app.scene.set_entity_transform("cube", transform);
+    }
+}
+
+#[pollster::main]
+async fn main() -> Result<(), WsgError> {
+    let app = AppBuilder::new().title("WSG Spot Test").build().await?;
+    app.run(SpotTest {
+        angle_x: 0.0,
+        angle_y: 0.0,
+    })
+}