This example is running in WebGL2 and should work in most browsers. You can check the WebGPU examples here.
//! Demonstrates how to use the [`MeshRayCast`] system parameter to chain multiple ray casts
//! and bounce off of surfaces.
use std::f32::consts::{FRAC_PI_2, PI};
use bevy::{
color::palettes::css,
core_pipeline::{bloom::Bloom, tonemapping::Tonemapping},
math::vec3,
picking::backend::ray::RayMap,
prelude::*,
};
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.add_systems(Startup, setup)
.add_systems(Update, bouncing_raycast)
.insert_resource(ClearColor(Color::BLACK))
.run();
}
const MAX_BOUNCES: usize = 64;
const LASER_SPEED: f32 = 0.03;
fn bouncing_raycast(
mut ray_cast: MeshRayCast,
mut gizmos: Gizmos,
time: Res<Time>,
// The ray map stores rays cast by the cursor
ray_map: Res<RayMap>,
) {
// Cast an automatically moving ray and bounce it off of surfaces
let t = ops::cos((time.elapsed_secs() - 4.0).max(0.0) * LASER_SPEED) * PI;
let ray_pos = Vec3::new(ops::sin(t), ops::cos(3.0 * t) * 0.5, ops::cos(t)) * 0.5;
let ray_dir = Dir3::new(-ray_pos).unwrap();
let ray = Ray3d::new(ray_pos, ray_dir);
gizmos.sphere(ray_pos, 0.1, Color::WHITE);
bounce_ray(ray, &mut ray_cast, &mut gizmos, Color::from(css::RED));
// Cast a ray from the cursor and bounce it off of surfaces
for (_, ray) in ray_map.iter() {
bounce_ray(*ray, &mut ray_cast, &mut gizmos, Color::from(css::GREEN));
}
}
// Bounces a ray off of surfaces `MAX_BOUNCES` times.
fn bounce_ray(mut ray: Ray3d, ray_cast: &mut MeshRayCast, gizmos: &mut Gizmos, color: Color) {
let mut intersections = Vec::with_capacity(MAX_BOUNCES + 1);
intersections.push((ray.origin, Color::srgb(30.0, 0.0, 0.0)));
for i in 0..MAX_BOUNCES {
// Cast the ray and get the first hit
let Some((_, hit)) = ray_cast.cast_ray(ray, &RayCastSettings::default()).first() else {
break;
};
// Draw the point of intersection and add it to the list
let brightness = 1.0 + 10.0 * (1.0 - i as f32 / MAX_BOUNCES as f32);
intersections.push((hit.point, Color::BLACK.mix(&color, brightness)));
gizmos.sphere(hit.point, 0.005, Color::BLACK.mix(&color, brightness * 2.0));
// Reflect the ray off of the surface
ray.direction = Dir3::new(ray.direction.reflect(hit.normal)).unwrap();
ray.origin = hit.point + ray.direction * 1e-6;
}
gizmos.linestrip_gradient(intersections);
}
// Set up a simple 3D scene
fn setup(
mut commands: Commands,
mut meshes: ResMut<Assets<Mesh>>,
mut materials: ResMut<Assets<StandardMaterial>>,
) {
// Make a box of planes facing inward so the laser gets trapped inside
let plane_mesh = meshes.add(Plane3d::default());
let plane_material = materials.add(Color::from(css::GRAY).with_alpha(0.01));
let create_plane = move |translation, rotation| {
(
Transform::from_translation(translation)
.with_rotation(Quat::from_scaled_axis(rotation)),
Mesh3d(plane_mesh.clone()),
MeshMaterial3d(plane_material.clone()),
)
};
commands.spawn(create_plane(vec3(0.0, 0.5, 0.0), Vec3::X * PI));
commands.spawn(create_plane(vec3(0.0, -0.5, 0.0), Vec3::ZERO));
commands.spawn(create_plane(vec3(0.5, 0.0, 0.0), Vec3::Z * FRAC_PI_2));
commands.spawn(create_plane(vec3(-0.5, 0.0, 0.0), Vec3::Z * -FRAC_PI_2));
commands.spawn(create_plane(vec3(0.0, 0.0, 0.5), Vec3::X * -FRAC_PI_2));
commands.spawn(create_plane(vec3(0.0, 0.0, -0.5), Vec3::X * FRAC_PI_2));
// Light
commands.spawn((
DirectionalLight::default(),
Transform::from_rotation(Quat::from_euler(EulerRot::XYZ, -0.1, 0.2, 0.0)),
));
// Camera
commands.spawn((
Camera3d::default(),
Camera {
hdr: true,
..default()
},
Transform::from_xyz(1.5, 1.5, 1.5).looking_at(Vec3::ZERO, Vec3::Y),
Tonemapping::TonyMcMapface,
Bloom::default(),
));
}