1#define_import_path bevy_gaussian_splatting::spherical_harmonics
2
3const shc = array<f32, 16>(
4    0.28209479177387814,
5    -0.4886025119029199,
6    0.4886025119029199,
7    -0.4886025119029199,
8    1.0925484305920792,
9    -1.0925484305920792,
10    0.31539156525252005,
11    -1.0925484305920792,
12    0.5462742152960396,
13    -0.5900435899266435,
14    2.890611442640554,
15    -0.4570457994644658,
16    0.3731763325901154,
17    -0.4570457994644658,
18    1.445305721320277,
19    -0.5900435899266435,
20);
21
22fn srgb_to_linear(srgb_color: vec3<f32>) -> vec3<f32> {
23    var linear_color: vec3<f32>;
24    for (var i = 0u; i < 3u; i = i + 1u) {
25        if (srgb_color[i] <= 0.04045) {
26            linear_color[i] = srgb_color[i] / 12.92;
27        } else {
28            linear_color[i] = pow((srgb_color[i] + 0.055) / 1.055, 2.4);
29        }
30    }
31    return linear_color;
32}
33
34fn spherical_harmonics_lookup(
35    ray_direction: vec3<f32>,
36    sh: array<f32, #{SH_COEFF_COUNT}>,
37) -> vec3<f32> {
38    let rds = ray_direction * ray_direction;
39    var color = vec3<f32>(0.5);
40
41    color += shc[ 0] * vec3<f32>(sh[0], sh[1], sh[2]);
42
43#if SH_COEFF_COUNT > 11
44    color += shc[ 1] * vec3<f32>(sh[ 3], sh[ 4], sh[ 5]) * ray_direction.y;
45    color += shc[ 2] * vec3<f32>(sh[ 6], sh[ 7], sh[ 8]) * ray_direction.z;
46    color += shc[ 3] * vec3<f32>(sh[ 9], sh[10], sh[11]) * ray_direction.x;
47#endif
48
49#if SH_COEFF_COUNT > 26
50    color += shc[ 4] * vec3<f32>(sh[12], sh[13], sh[14]) * ray_direction.x * ray_direction.y;
51    color += shc[ 5] * vec3<f32>(sh[15], sh[16], sh[17]) * ray_direction.y * ray_direction.z;
52    color += shc[ 6] * vec3<f32>(sh[18], sh[19], sh[20]) * (2.0 * rds.z - rds.x - rds.y);
53    color += shc[ 7] * vec3<f32>(sh[21], sh[22], sh[23]) * ray_direction.x * ray_direction.z;
54    color += shc[ 8] * vec3<f32>(sh[24], sh[25], sh[26]) * (rds.x - rds.y);
55#endif
56
57#if SH_COEFF_COUNT > 47
58    color += shc[ 9] * vec3<f32>(sh[27], sh[28], sh[29]) * ray_direction.y * (3.0 * rds.x - rds.y);
59    color += shc[10] * vec3<f32>(sh[30], sh[31], sh[32]) * ray_direction.x * ray_direction.y * ray_direction.z;
60    color += shc[11] * vec3<f32>(sh[33], sh[34], sh[35]) * ray_direction.y * (4.0 * rds.z - rds.x - rds.y);
61    color += shc[12] * vec3<f32>(sh[36], sh[37], sh[38]) * ray_direction.z * (2.0 * rds.z - 3.0 * rds.x - 3.0 * rds.y);
62    color += shc[13] * vec3<f32>(sh[39], sh[40], sh[41]) * ray_direction.x * (4.0 * rds.z - rds.x - rds.y);
63    color += shc[14] * vec3<f32>(sh[42], sh[43], sh[44]) * ray_direction.z * (rds.x - rds.y);
64    color += shc[15] * vec3<f32>(sh[45], sh[46], sh[47]) * ray_direction.x * (rds.x - 3.0 * rds.y);
65#endif
66
67    return color;
68}