decal/
decal.rs

1//! Decal rendering.
2//! Note: On Wasm, this example only runs on WebGPU
3
4use bevy::{
5    camera_controller::free_camera::{FreeCamera, FreeCameraPlugin},
6    core_pipeline::prepass::DepthPrepass,
7    pbr::decal::{ForwardDecal, ForwardDecalMaterial, ForwardDecalMaterialExt},
8    prelude::*,
9};
10use chacha20::ChaCha8Rng;
11use rand::{RngExt, SeedableRng};
12
13fn main() {
14    App::new()
15        .add_plugins((DefaultPlugins, FreeCameraPlugin))
16        .add_systems(Startup, setup)
17        .run();
18}
19
20fn setup(
21    mut commands: Commands,
22    mut meshes: ResMut<Assets<Mesh>>,
23    mut standard_materials: ResMut<Assets<StandardMaterial>>,
24    mut decal_standard_materials: ResMut<Assets<ForwardDecalMaterial<StandardMaterial>>>,
25    asset_server: Res<AssetServer>,
26) {
27    // Spawn the forward decal
28    commands.spawn((
29        Name::new("Decal"),
30        ForwardDecal,
31        MeshMaterial3d(decal_standard_materials.add(ForwardDecalMaterial {
32            base: StandardMaterial {
33                base_color_texture: Some(asset_server.load("textures/uv_checker_bw.png")),
34                ..default()
35            },
36            extension: ForwardDecalMaterialExt {
37                depth_fade_factor: 1.0,
38            },
39        })),
40        Transform::from_scale(Vec3::splat(4.0)),
41    ));
42
43    commands.spawn((
44        Name::new("Camera"),
45        Camera3d::default(),
46        FreeCamera::default(),
47        // Must enable the depth prepass to render forward decals
48        DepthPrepass,
49        Transform::from_xyz(2.0, 9.5, 2.5).looking_at(Vec3::ZERO, Vec3::Y),
50    ));
51
52    let white_material = standard_materials.add(Color::WHITE);
53
54    commands.spawn((
55        Name::new("Floor"),
56        Mesh3d(meshes.add(Rectangle::from_length(10.0))),
57        MeshMaterial3d(white_material.clone()),
58        Transform::from_rotation(Quat::from_rotation_x(-std::f32::consts::FRAC_PI_2)),
59    ));
60
61    // Spawn a few cube with random rotations to showcase how the decals behave with non-flat geometry
62    let num_obs = 10;
63    let mut rng = ChaCha8Rng::seed_from_u64(19878367467713);
64    for i in 0..num_obs {
65        for j in 0..num_obs {
66            let rotation_axis: [f32; 3] = rng.random();
67            let rotation_vec: Vec3 = rotation_axis.into();
68            let rotation: u32 = rng.random_range(0..360);
69            let transform = Transform::from_xyz(
70                (-num_obs + 1) as f32 / 2.0 + i as f32,
71                -0.2,
72                (-num_obs + 1) as f32 / 2.0 + j as f32,
73            )
74            .with_rotation(Quat::from_axis_angle(
75                rotation_vec.normalize_or_zero(),
76                (rotation as f32).to_radians(),
77            ));
78
79            commands.spawn((
80                Mesh3d(meshes.add(Cuboid::from_length(0.6))),
81                MeshMaterial3d(white_material.clone()),
82                transform,
83            ));
84        }
85    }
86
87    commands.spawn((
88        Name::new("Light"),
89        PointLight {
90            shadow_maps_enabled: true,
91            ..default()
92        },
93        Transform::from_xyz(4.0, 8.0, 4.0),
94    ));
95}
decal/decal.rs

decal/
decal.rs
