1// The time since startup data is in the globals binding which is part of the mesh_view_bindings import
2import bevy_pbr::render::{
3    mesh_view_bindings::globals,
4    forward_io::VertexOutput,
5};
6
7fn oklab_to_linear_srgb(c: vec3<f32>) -> vec3<f32> {
8    let L = c.x;
9    let a = c.y;
10    let b = c.z;
11
12    let l_ = L + 0.3963377774 * a + 0.2158037573 * b;
13    let m_ = L - 0.1055613458 * a - 0.0638541728 * b;
14    let s_ = L - 0.0894841775 * a - 1.2914855480 * b;
15
16    let l = l_ * l_ * l_;
17    let m = m_ * m_ * m_;
18    let s = s_ * s_ * s_;
19
20    return vec3<f32>(
21        4.0767416621 * l - 3.3077115913 * m + 0.2309699292 * s,
22        -1.2684380046 * l + 2.6097574011 * m - 0.3413193965 * s,
23        -0.0041960863 * l - 0.7034186147 * m + 1.7076147010 * s,
24    );
25}
26
27@fragment
28fn fragment(in: VertexOutput) -> @location(0) vec4<f32> {
29    let speed = 2.0;
30    // The globals binding contains various global values like time
31    // which is the time since startup in seconds
32    let t_1 = sin(globals.time * speed) * 0.5 + 0.5;
33    let t_2 = cos(globals.time * speed);
34
35    let distance_to_center = distance(in.uv, vec2<f32>(0.5)) * 1.4;
36
37    // blending is done in a perceptual color space: https://bottosson.github.io/posts/oklab/
38    let red = vec3<f32>(0.627955, 0.224863, 0.125846);
39    let green = vec3<f32>(0.86644, -0.233887, 0.179498);
40    let blue = vec3<f32>(0.701674, 0.274566, -0.169156);
41    let white = vec3<f32>(1.0, 0.0, 0.0);
42    let mixed = mix(mix(red, blue, t_1), mix(green, white, t_2), distance_to_center);
43
44    return vec4<f32>(oklab_to_linear_srgb(mixed), 1.0);
45}