1import package::atmosphere::{
2    bindings::{view, settings},
3    bruneton_functions::sample_transmittance_lut_segment,
4    functions::{
5        sample_transmittance_lut,
6        sample_sky_view_lut, direction_world_to_atmosphere,
7        uv_to_ray_direction, uv_to_ndc, sample_aerial_view_lut,
8        sample_sun_radiance, ndc_to_camera_dist, raymarch_atmosphere, 
9        get_view_position, max_atmosphere_distance
10    },
11};
12
13import bevy_core_pipeline::fullscreen_vertex_shader::FullscreenVertexOutput;
14
15@if(DUAL_SOURCE_BLENDING)
16enable dual_source_blending;
17
18@if(MULTISAMPLED)
19@group(0) @binding(13) var depth_texture: texture_depth_multisampled_2d;
20@else
21@group(0) @binding(13) var depth_texture: texture_depth_2d;
22
23struct RenderSkyOutput {
24    @if(DUAL_SOURCE_BLENDING)
25    @location(0) @blend_src(0) inscattering: vec4<f32>,
26    @if(DUAL_SOURCE_BLENDING)
27    @location(0) @blend_src(1) transmittance: vec4<f32>,
28    @else
29    @location(0) inscattering: vec4<f32>,
30}
31
32@fragment
33fn main(in: FullscreenVertexOutput) -> RenderSkyOutput {
34    let depth = textureLoad(depth_texture, vec2<i32>(in.position.xy), 0);
35
36    let ray_dir_ws = uv_to_ray_direction(in.uv);
37    let world_pos = get_view_position();
38    let r = length(world_pos);
39    let up = normalize(world_pos);
40    let mu = dot(ray_dir_ws, up);
41    let max_samples = settings.sky_max_samples;
42    let should_raymarch = settings.rendering_method == 1u;
43
44    var transmittance: vec3<f32>;
45    var inscattering: vec3<f32>;
46
47    let sun_radiance = sample_sun_radiance(ray_dir_ws);
48
49    if depth == 0.0 {
50        let ray_dir_as = direction_world_to_atmosphere(ray_dir_ws);
51        transmittance = sample_transmittance_lut(r, mu);
52        inscattering = sample_sky_view_lut(r, ray_dir_as);
53        if should_raymarch {
54            let t_max = max_atmosphere_distance(r, mu);
55            let result = raymarch_atmosphere(world_pos, ray_dir_ws, t_max, max_samples, in.uv, true);
56            inscattering = result.inscattering;
57            transmittance = result.transmittance;
58        }
59        inscattering += sun_radiance * transmittance;
60    } else {
61        let t = ndc_to_camera_dist(vec3(uv_to_ndc(in.uv), depth));
62        inscattering = sample_aerial_view_lut(in.uv, t);
63        transmittance = sample_transmittance_lut_segment(r, mu, t);
64        if should_raymarch {
65            let result = raymarch_atmosphere(world_pos, ray_dir_ws, t, max_samples, in.uv, false);
66            inscattering = result.inscattering;
67            transmittance = result.transmittance;
68        }
69    }
70
71    // exposure compensation
72    inscattering *= view.exposure;
73    
74    @if(DUAL_SOURCE_BLENDING)
75    return RenderSkyOutput(vec4(inscattering, 0.0), vec4(transmittance, 1.0));
76    @if(!DUAL_SOURCE_BLENDING)
77    let mean_transmittance = (transmittance.r + transmittance.g + transmittance.b) / 3.0;
78    @if(!DUAL_SOURCE_BLENDING)
79    return RenderSkyOutput(vec4(inscattering, mean_transmittance));
80    
81}