1// This shader, a part of the `clustered_decals` example, shows how to use the
2// decal `tag` field to apply arbitrary decal effects.
3
4#import bevy_pbr::{
5    clustered_forward,
6    decal::clustered,
7    forward_io::{VertexOutput, FragmentOutput},
8    mesh_view_bindings,
9    pbr_fragment::pbr_input_from_standard_material,
10    pbr_functions::{alpha_discard, apply_pbr_lighting, main_pass_post_lighting_processing},
11}
12
13@fragment
14fn fragment(
15    in: VertexOutput,
16    @builtin(front_facing) is_front: bool,
17) -> FragmentOutput {
18    // Generate a `PbrInput` struct from the `StandardMaterial` bindings.
19    var pbr_input = pbr_input_from_standard_material(in, is_front);
20
21    // Alpha discard.
22    pbr_input.material.base_color = alpha_discard(pbr_input.material, pbr_input.material.base_color);
23
24    // Apply the normal decals.
25    clustered::apply_decals(&pbr_input);
26
27    // Here we tint the color based on the tag of the decal.
28    // We could optionally do other things, such as adjust the normal based on a normal map.
29    let view_z = clustered::get_view_z(in.world_position.xyz);
30    let is_orthographic = clustered::view_is_orthographic();
31    let cluster_index =
32        clustered_forward::view_fragment_cluster_index(in.position.xy, view_z, is_orthographic);
33    var clusterable_object_index_ranges =
34        clustered_forward::unpack_clusterable_object_index_ranges(cluster_index);
35    var decal_iterator = clustered::clustered_decal_iterator_new(
36        in.world_position.xyz,
37        &clusterable_object_index_ranges
38    );
39    while (clustered::clustered_decal_iterator_next(&decal_iterator)) {
40        var decal_base_color = textureSampleLevel(
41            mesh_view_bindings::clustered_decal_textures[decal_iterator.base_color_texture_index],
42            mesh_view_bindings::clustered_decal_sampler,
43            decal_iterator.uv,
44            0.0
45        );
46
47        switch (decal_iterator.tag) {
48            case 1u: {
49                // Tint with red.
50                decal_base_color = vec4(
51                    mix(pbr_input.material.base_color.rgb, vec3(1.0, 0.0, 0.0), 0.5),
52                    decal_base_color.a,
53                );
54            }
55            case 2u: {
56                // Tint with blue.
57                decal_base_color = vec4(
58                    mix(pbr_input.material.base_color.rgb, vec3(0.0, 0.0, 1.0), 0.5),
59                    decal_base_color.a,
60                );
61            }
62            default: {}
63        }
64
65        pbr_input.material.base_color = vec4(
66            mix(pbr_input.material.base_color.rgb, decal_base_color.rgb, decal_base_color.a),
67            pbr_input.material.base_color.a + decal_base_color.a
68        );
69    }
70
71    // Apply lighting.
72    var out: FragmentOutput;
73    out.color = apply_pbr_lighting(pbr_input);
74
75    // Apply in-shader post processing (fog, alpha-premultiply, and also
76    // tonemapping, debanding if the camera is non-HDR). Note this does not
77    // include fullscreen postprocessing effects like bloom.
78    out.color = main_pass_post_lighting_processing(pbr_input, out.color);
79
80    return out;
81}
82