1//! Example of a fragment shader for a custom material setup to correctly handle
2//! order independent transparency.
3//! See examples/3d/order_independent_transpatency.rs
4
5// As an hard-coded always transparent material it is only meant to be forward rendered
6import bevy_pbr::render::forward_io::{VertexOutput, FragmentOutput};
7import bevy_pbr::render::utils;
8
9@if(MATERIAL_OIT_ENABLED)
10import bevy_core_pipeline::oit::draw::oit_draw;
11
12@group(constants::MATERIAL_BIND_GROUP) @binding(0) var<uniform> material_color: vec4<f32>;
13
14@fragment
15fn fragment(
16    in: VertexOutput,
17) -> @location(0) vec4<f32> {
18
19    // This produces a noise-like varying transparency.
20    // Using world coordinates for simplicity, but local mesh coordinates
21    // would be required if the mesh moved.
22    let alpha = gradient_noise(in.world_position.xyz, 5.0);
23    let color = vec4f(material_color.rgb, alpha);
24
25@if(MATERIAL_OIT_ENABLED) {
26    // The input color of `oit_draw` should be alpha-premultiplied.
27    oit_draw(in.position, vec4f(color.rgb * color.a, color.a));
28    discard;
29}
30
31    return color;
32}
33
34fn gradient_noise(coord: vec3f, scale: f32) -> f32 {
35    let grid_coord = vec3u(scale * abs(coord));
36    let f = fract(scale * abs(coord));
37
38    let g0 = rand3(grid_coord + vec3u(0, 0, 0));
39    let g1 = rand3(grid_coord + vec3u(1, 0, 0));
40    let g2 = rand3(grid_coord + vec3u(0, 1, 0));
41    let g3 = rand3(grid_coord + vec3u(1, 1, 0));
42    let g4 = rand3(grid_coord + vec3u(0, 0, 1));
43    let g5 = rand3(grid_coord + vec3u(1, 0, 1));
44    let g6 = rand3(grid_coord + vec3u(0, 1, 1));
45    let g7 = rand3(grid_coord + vec3u(1, 1, 1));
46
47    let noise = mix(
48                    mix(
49                        mix(dot(g0, f - vec3f(0.0, 0.0, 0.0)),
50                            dot(g1, f - vec3f(1.0, 0.0, 0.0)), f.x),
51                        mix(dot(g2, f - vec3f(0.0, 1.0, 0.0)),
52                            dot(g3, f - vec3f(1.0, 1.0, 0.0)), f.x),
53                        f.y),
54                    mix(
55                        mix(dot(g4, f - vec3f(0.0, 0.0, 1.0)),
56                            dot(g5, f - vec3f(1.0, 0.0, 1.0)), f.x),
57                        mix(dot(g6, f - vec3f(0.0, 1.0, 1.0)),
58                            dot(g7, f - vec3f(1.0, 1.0, 1.0)), f.x),
59                        f.y),
60                    f.z);
61
62    return noise;
63}
64
65fn rand3(seed: vec3u) -> vec3f {
66    var rng: u32 = (seed.x * 3966231743u) ^ (seed.y * 3928936651u) ^ (seed.z * 53134757u);
67    return rand_vec3f(&rng);
68}
69
70fn rand_vec3f(state: ptr<function, u32>) -> vec3<f32> {
71    return vec3f(utils::rand_f(state), utils::rand_f(state), utils::rand_f(state));
72}