1import bevy_pbr::render::{
2    mesh_view_bindings,
3    forward_io::VertexOutput,
4};
5
6import bevy_render::maths::PI;
7
8@if(TONEMAP_IN_SHADER)
9import bevy_core_pipeline::tonemapping::tone_mapping;
10
11/// Sweep across hues on y axis with value from 0.0 to +15EV across x axis
12/// quantized into 24 steps for both axis.
13fn color_sweep(uv_input: vec2<f32>) -> vec3<f32> {
14    var uv = uv_input;
15    let steps = 24.0;
16    uv.y = uv.y * (1.0 + 1.0 / steps);
17    let ratio = 2.0;
18
19    let h = PI * 2.0 * floor(1.0 + steps * uv.y) / steps;
20    let L = floor(uv.x * steps * ratio) / (steps * ratio) - 0.5;
21
22    var color = vec3(0.0);
23    if uv.y < 1.0 {
24        color = cos(h + vec3(0.0, 1.0, 2.0) * PI * 2.0 / 3.0);
25        let maxRGB = max(color.r, max(color.g, color.b));
26        let minRGB = min(color.r, min(color.g, color.b));
27        color = exp(15.0 * L) * (color - minRGB) / (maxRGB - minRGB);
28    } else {
29        color = vec3(exp(15.0 * L));
30    }
31    return color;
32}
33
34fn hsv_to_srgb(c: vec3<f32>) -> vec3<f32> {
35    let K = vec4(1.0, 2.0 / 3.0, 1.0 / 3.0, 3.0);
36    let p = abs(fract(c.xxx + K.xyz) * 6.0 - K.www);
37    return c.z * mix(K.xxx, clamp(p - K.xxx, vec3(0.0), vec3(1.0)), c.y);
38}
39
40/// Generates a continuous sRGB sweep.
41fn continuous_hue(uv: vec2<f32>) -> vec3<f32> {
42    return hsv_to_srgb(vec3(uv.x, 1.0, 1.0)) * max(0.0, exp2(uv.y * 9.0) - 1.0);
43}
44
45@fragment
46fn fragment(
47    in: VertexOutput,
48) -> @location(0) vec4<f32> {
49    var uv = in.uv;
50    var out = vec3(0.0);
51    if uv.y > 0.5 {
52        uv.y = 1.0 - uv.y;
53        out = color_sweep(vec2(uv.x, uv.y * 2.0));
54    } else {
55        out = continuous_hue(vec2(uv.y * 2.0, uv.x));
56    }
57    var color = vec4(out, 1.0);
58    @if(TONEMAP_IN_SHADER)
59    color = tone_mapping(color, mesh_view_bindings::view.color_grading);
60    return color;
61}