1#import bevy_core_pipeline::tonemapping::tonemapping_luminance as luminance
2#import bevy_pbr::utils::{rand_f, rand_range_u, sample_cosine_hemisphere}
3#import bevy_render::view::View
4#import bevy_solari::presample_light_tiles::{ResolvedLightSamplePacked, unpack_resolved_light_sample}
5#import bevy_solari::sampling::{calculate_resolved_light_contribution, trace_light_visibility}
6#import bevy_solari::scene_bindings::{trace_ray, resolve_ray_hit_full, RAY_T_MIN}
7#import bevy_solari::world_cache::{
8    WORLD_CACHE_MAX_TEMPORAL_SAMPLES,
9    WORLD_CACHE_DIRECT_LIGHT_SAMPLE_COUNT,
10    WORLD_CACHE_MAX_GI_RAY_DISTANCE,
11    query_world_cache,
12    world_cache_active_cells_count,
13    world_cache_active_cell_indices,
14    world_cache_life,
15    world_cache_geometry_data,
16    world_cache_radiance,
17    world_cache_luminance_deltas,
18    world_cache_active_cells_new_radiance,
19}
20
21@group(1) @binding(2) var<storage, read_write> light_tile_resolved_samples: array<ResolvedLightSamplePacked>;
22@group(1) @binding(12) var<uniform> view: View;
23struct PushConstants { frame_index: u32, reset: u32 }
24var<push_constant> constants: PushConstants;
25
26@compute @workgroup_size(64, 1, 1)
27fn sample_radiance(@builtin(workgroup_id) workgroup_id: vec3<u32>, @builtin(global_invocation_id) active_cell_id: vec3<u32>) {
28    if active_cell_id.x < world_cache_active_cells_count {
29        let cell_index = world_cache_active_cell_indices[active_cell_id.x];
30        let geometry_data = world_cache_geometry_data[cell_index];
31        var rng = cell_index + constants.frame_index;
32
33        // TODO: Initialize newly active cells with data from an adjacent LOD
34
35        var new_radiance = sample_random_light_ris(geometry_data.world_position, geometry_data.world_normal, workgroup_id.xy, &rng);
36
37#ifndef NO_MULTIBOUNCE
38        let ray_direction = sample_cosine_hemisphere(geometry_data.world_normal, &rng);
39        let ray_hit = trace_ray(geometry_data.world_position, ray_direction, RAY_T_MIN, WORLD_CACHE_MAX_GI_RAY_DISTANCE, RAY_FLAG_NONE);
40        if ray_hit.kind != RAY_QUERY_INTERSECTION_NONE {
41            let ray_hit = resolve_ray_hit_full(ray_hit);
42            let cell_life = atomicLoad(&world_cache_life[cell_index]);
43            new_radiance += ray_hit.material.base_color * query_world_cache(ray_hit.world_position, ray_hit.geometric_world_normal, view.world_position, cell_life, &rng);
44        }
45#endif
46
47        world_cache_active_cells_new_radiance[active_cell_id.x] = new_radiance;
48    }
49}
50
51@compute @workgroup_size(64, 1, 1)
52fn blend_new_samples(@builtin(global_invocation_id) active_cell_id: vec3<u32>) {
53    if active_cell_id.x < world_cache_active_cells_count {
54        let cell_index = world_cache_active_cell_indices[active_cell_id.x];
55
56        let old_radiance = world_cache_radiance[cell_index];
57        let new_radiance = world_cache_active_cells_new_radiance[active_cell_id.x];
58        let luminance_delta = world_cache_luminance_deltas[cell_index];
59
60        // https://bsky.app/profile/gboisse.bsky.social/post/3m5blga3ftk2a
61        let sample_count = min(old_radiance.a + 1.0, WORLD_CACHE_MAX_TEMPORAL_SAMPLES);
62        let alpha = abs(luminance_delta) / max(luminance(old_radiance.rgb), 0.001);
63        let max_sample_count = mix(WORLD_CACHE_MAX_TEMPORAL_SAMPLES, 1.0, pow(saturate(alpha), 1.0 / 8.0));
64        let blend_amount = 1.0 / min(sample_count, max_sample_count);
65
66        let blended_radiance = mix(old_radiance.rgb, new_radiance, blend_amount);
67        let blended_luminance_delta = mix(luminance_delta, luminance(blended_radiance) - luminance(old_radiance.rgb), 1.0 / 8.0);
68
69        world_cache_radiance[cell_index] = vec4(blended_radiance, sample_count);
70        world_cache_luminance_deltas[cell_index] = blended_luminance_delta;
71    }
72}
73
74fn sample_random_light_ris(world_position: vec3<f32>, world_normal: vec3<f32>, workgroup_id: vec2<u32>, rng: ptr<function, u32>) -> vec3<f32> {
75    var workgroup_rng = (workgroup_id.x * 5782582u) + workgroup_id.y;
76    let light_tile_start = rand_range_u(128u, &workgroup_rng) * 1024u;
77
78    var weight_sum = 0.0;
79    var selected_sample_radiance = vec3(0.0);
80    var selected_sample_target_function = 0.0;
81    var selected_sample_world_position = vec4(0.0);
82    let mis_weight = 1.0 / f32(WORLD_CACHE_DIRECT_LIGHT_SAMPLE_COUNT);
83    for (var i = 0u; i < WORLD_CACHE_DIRECT_LIGHT_SAMPLE_COUNT; i++) {
84        let tile_sample = light_tile_start + rand_range_u(1024u, rng);
85        let resolved_light_sample = unpack_resolved_light_sample(light_tile_resolved_samples[tile_sample], view.exposure);
86        let light_contribution = calculate_resolved_light_contribution(resolved_light_sample, world_position, world_normal);
87
88        let target_function = luminance(light_contribution.radiance);
89        let resampling_weight = mis_weight * (target_function * light_contribution.inverse_pdf);
90
91        weight_sum += resampling_weight;
92
93        if rand_f(rng) < resampling_weight / weight_sum {
94            selected_sample_radiance = light_contribution.radiance;
95            selected_sample_target_function = target_function;
96            selected_sample_world_position = resolved_light_sample.world_position;
97        }
98    }
99
100    var unbiased_contribution_weight = 0.0;
101    if all(selected_sample_radiance != vec3(0.0)) {
102        let inverse_target_function = select(0.0, 1.0 / selected_sample_target_function, selected_sample_target_function > 0.0);
103        unbiased_contribution_weight = weight_sum * inverse_target_function;
104
105        unbiased_contribution_weight *= trace_light_visibility(world_position, selected_sample_world_position);
106    }
107
108    return selected_sample_radiance * unbiased_contribution_weight;
109}