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    pbr_input.material.base_color = clustered::apply_decal_base_color(
26        in.world_position.xyz,
27        in.position.xy,
28        pbr_input.material.base_color
29    );
30
31    // Here we tint the color based on the tag of the decal.
32    // We could optionally do other things, such as adjust the normal based on a normal map.
33    let view_z = clustered::get_view_z(in.world_position.xyz);
34    let is_orthographic = clustered::view_is_orthographic();
35    let cluster_index =
36        clustered_forward::fragment_cluster_index(in.position.xy, view_z, is_orthographic);
37    var clusterable_object_index_ranges =
38        clustered_forward::unpack_clusterable_object_index_ranges(cluster_index);
39    var decal_iterator = clustered::clustered_decal_iterator_new(
40        in.world_position.xyz,
41        &clusterable_object_index_ranges
42    );
43    while (clustered::clustered_decal_iterator_next(&decal_iterator)) {
44        var decal_base_color = textureSampleLevel(
45            mesh_view_bindings::clustered_decal_textures[decal_iterator.texture_index],
46            mesh_view_bindings::clustered_decal_sampler,
47            decal_iterator.uv,
48            0.0
49        );
50
51        switch (decal_iterator.tag) {
52            case 1u: {
53                // Tint with red.
54                decal_base_color = vec4(
55                    mix(pbr_input.material.base_color.rgb, vec3(1.0, 0.0, 0.0), 0.5),
56                    decal_base_color.a,
57                );
58            }
59            case 2u: {
60                // Tint with blue.
61                decal_base_color = vec4(
62                    mix(pbr_input.material.base_color.rgb, vec3(0.0, 0.0, 1.0), 0.5),
63                    decal_base_color.a,
64                );
65            }
66            default: {}
67        }
68
69        pbr_input.material.base_color = vec4(
70            mix(pbr_input.material.base_color.rgb, decal_base_color.rgb, decal_base_color.a),
71            pbr_input.material.base_color.a + decal_base_color.a
72        );
73    }
74
75    // Apply lighting.
76    var out: FragmentOutput;
77    out.color = apply_pbr_lighting(pbr_input);
78
79    // Apply in-shader post processing (fog, alpha-premultiply, and also
80    // tonemapping, debanding if the camera is non-HDR). Note this does not
81    // include fullscreen postprocessing effects like bloom.
82    out.color = main_pass_post_lighting_processing(pbr_input, out.color);
83
84    return out;
85}
86