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
4import bevy_pbr::{
5    decal::clustered,
6    render::{
7        clustered_forward,
8        forward_io::{VertexOutput, FragmentOutput},
9        mesh_view_bindings,
10        pbr_fragment::pbr_input_from_standard_material,
11        pbr_functions::{alpha_discard, apply_pbr_lighting, main_pass_post_lighting_processing},
12    },
13};
14
15@fragment
16fn fragment(
17    in: VertexOutput,
18    @builtin(front_facing) is_front: bool,
19) -> FragmentOutput {
20    // Generate a `PbrInput` struct from the `StandardMaterial` bindings.
21    var pbr_input = pbr_input_from_standard_material(in, is_front);
22
23    // Alpha discard.
24    pbr_input.material.base_color = alpha_discard(
25        pbr_input.material.flags,
26        pbr_input.material.alpha_cutoff,
27        pbr_input.material.base_color,
28    );
29
30    // Apply the normal decals.
31    clustered::apply_decals(&pbr_input);
32
33    // Here we tint the color based on the tag of the decal.
34    // We could optionally do other things, such as adjust the normal based on a normal map.
35    let view_z = clustered::get_view_z(in.world_position.xyz);
36    let is_orthographic = clustered::view_is_orthographic();
37    let cluster_index =
38        clustered_forward::view_fragment_cluster_index(in.position.xy, view_z, is_orthographic);
39    var clusterable_object_index_ranges =
40        clustered_forward::unpack_clusterable_object_index_ranges(cluster_index);
41    var decal_iterator = clustered::clustered_decal_iterator_new(
42        in.world_position.xyz,
43        &clusterable_object_index_ranges
44    );
45    while (clustered::clustered_decal_iterator_next(&decal_iterator)) {
46        var decal_base_color = textureSampleLevel(
47            mesh_view_bindings::clustered_decal_textures[decal_iterator.base_color_texture_index],
48            mesh_view_bindings::clustered_decal_sampler,
49            decal_iterator.uv,
50            0.0
51        );
52
53        switch (decal_iterator.tag) {
54            case 1u: {
55                // Tint with red.
56                decal_base_color = vec4(
57                    mix(pbr_input.material.base_color.rgb, vec3(1.0, 0.0, 0.0), 0.5),
58                    decal_base_color.a,
59                );
60            }
61            case 2u: {
62                // Tint with blue.
63                decal_base_color = vec4(
64                    mix(pbr_input.material.base_color.rgb, vec3(0.0, 0.0, 1.0), 0.5),
65                    decal_base_color.a,
66                );
67            }
68            default: {}
69        }
70
71        pbr_input.material.base_color = vec4(
72            mix(pbr_input.material.base_color.rgb, decal_base_color.rgb, decal_base_color.a),
73            pbr_input.material.base_color.a + decal_base_color.a
74        );
75    }
76
77    // Apply lighting.
78    var out: FragmentOutput;
79    out.color = apply_pbr_lighting(pbr_input);
80
81    // Apply in-shader post processing (fog, alpha-premultiply, and also
82    // tonemapping, debanding if the camera is non-HDR). Note this does not
83    // include fullscreen postprocessing effects like bloom.
84    out.color = main_pass_post_lighting_processing(pbr_input, out.color);
85
86    return out;
87}