1#import bevy_pbr::{
2    atmosphere::{
3        functions::{direction_world_to_atmosphere, sample_sky_view_lut, get_view_position},
4    },
5    utils::sample_cube_dir
6}
7
8@group(0) @binding(13) var output: texture_storage_2d_array<rgba16float, write>;
9
10@compute @workgroup_size(8, 8, 1)
11fn main(@builtin(global_invocation_id) global_id: vec3<u32>) {
12    let dimensions = textureDimensions(output);
13    let slice_index = global_id.z;
14    
15    if (global_id.x >= dimensions.x || global_id.y >= dimensions.y || slice_index >= 6u) {
16        return;
17    }
18    
19    // Calculate normalized UV coordinates for this pixel
20    let uv = vec2<f32>(
21        (f32(global_id.x) + 0.5) / f32(dimensions.x),
22        (f32(global_id.y) + 0.5) / f32(dimensions.y)
23    );
24
25    var ray_dir_ws = sample_cube_dir(uv, slice_index);
26    
27    // invert the z direction to account for cubemaps being lefthanded
28    ray_dir_ws.z = -ray_dir_ws.z;
29
30    let world_pos = get_view_position();
31    let r = length(world_pos);
32    let up = normalize(world_pos);
33
34    let ray_dir_as = direction_world_to_atmosphere(ray_dir_ws.xyz, up);
35    let inscattering = sample_sky_view_lut(r, ray_dir_as);
36    let color = vec4<f32>(inscattering, 1.0);
37
38    textureStore(output, vec2<i32>(global_id.xy), i32(slice_index), color);
39}