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