1// 3x3 bilaterial filter (edge-preserving blur)
2// https://people.csail.mit.edu/sparis/bf_course/course_notes.pdf
3
4// Note: Does not use the Gaussian kernel part of a typical bilateral blur
5// From the paper: "use the information gathered on a neighborhood of 4 × 4 using a bilateral filter for
6// reconstruction, using _uniform_ convolution weights"
7
8// Note: The paper does a 4x4 (not quite centered) filter, offset by +/- 1 pixel every other frame
9// XeGTAO does a 3x3 filter, on two pixels at a time per compute thread, applied twice
10// We do a 3x3 filter, on 1 pixel per compute thread, applied once
11
12#import bevy_render::view::View
13
14@group(0) @binding(0) var ambient_occlusion_noisy: texture_2d<f32>;
15@group(0) @binding(1) var depth_differences: texture_2d<u32>;
16@group(0) @binding(2) var ambient_occlusion: texture_storage_2d<r16float, write>;
17@group(1) @binding(0) var point_clamp_sampler: sampler;
18@group(1) @binding(1) var linear_clamp_sampler: sampler;
19@group(1) @binding(2) var<uniform> view: View;
20
21@compute
22@workgroup_size(8, 8, 1)
23fn spatial_denoise(@builtin(global_invocation_id) global_id: vec3<u32>) {
24    let pixel_coordinates = vec2<i32>(global_id.xy);
25    let uv = vec2<f32>(pixel_coordinates) / view.viewport.zw;
26
27    let edges0 = textureGather(0, depth_differences, point_clamp_sampler, uv);
28    let edges1 = textureGather(0, depth_differences, point_clamp_sampler, uv, vec2<i32>(2i, 0i));
29    let edges2 = textureGather(0, depth_differences, point_clamp_sampler, uv, vec2<i32>(1i, 2i));
30    let visibility0 = textureGather(0, ambient_occlusion_noisy, point_clamp_sampler, uv);
31    let visibility1 = textureGather(0, ambient_occlusion_noisy, point_clamp_sampler, uv, vec2<i32>(2i, 0i));
32    let visibility2 = textureGather(0, ambient_occlusion_noisy, point_clamp_sampler, uv, vec2<i32>(0i, 2i));
33    let visibility3 = textureGather(0, ambient_occlusion_noisy, point_clamp_sampler, uv, vec2<i32>(2i, 2i));
34
35    let left_edges = unpack4x8unorm(edges0.x);
36    let right_edges = unpack4x8unorm(edges1.x);
37    let top_edges = unpack4x8unorm(edges0.z);
38    let bottom_edges = unpack4x8unorm(edges2.w);
39    var center_edges = unpack4x8unorm(edges0.y);
40    center_edges *= vec4<f32>(left_edges.y, right_edges.x, top_edges.w, bottom_edges.z);
41
42    let center_weight = 1.2;
43    let left_weight = center_edges.x;
44    let right_weight = center_edges.y;
45    let top_weight = center_edges.z;
46    let bottom_weight = center_edges.w;
47    let top_left_weight = 0.425 * (top_weight * top_edges.x + left_weight * left_edges.z);
48    let top_right_weight = 0.425 * (top_weight * top_edges.y + right_weight * right_edges.z);
49    let bottom_left_weight = 0.425 * (bottom_weight * bottom_edges.x + left_weight * left_edges.w);
50    let bottom_right_weight = 0.425 * (bottom_weight * bottom_edges.y + right_weight * right_edges.w);
51
52    let center_visibility = visibility0.y;
53    let left_visibility = visibility0.x;
54    let right_visibility = visibility0.z;
55    let top_visibility = visibility1.x;
56    let bottom_visibility = visibility2.z;
57    let top_left_visibility = visibility0.w;
58    let top_right_visibility = visibility1.w;
59    let bottom_left_visibility = visibility2.w;
60    let bottom_right_visibility = visibility3.w;
61
62    var sum = center_visibility;
63    sum += left_visibility * left_weight;
64    sum += right_visibility * right_weight;
65    sum += top_visibility * top_weight;
66    sum += bottom_visibility * bottom_weight;
67    sum += top_left_visibility * top_left_weight;
68    sum += top_right_visibility * top_right_weight;
69    sum += bottom_left_visibility * bottom_left_weight;
70    sum += bottom_right_visibility * bottom_right_weight;
71
72    var sum_weight = center_weight;
73    sum_weight += left_weight;
74    sum_weight += right_weight;
75    sum_weight += top_weight;
76    sum_weight += bottom_weight;
77    sum_weight += top_left_weight;
78    sum_weight += top_right_weight;
79    sum_weight += bottom_left_weight;
80    sum_weight += bottom_right_weight;
81
82    let denoised_visibility = sum / sum_weight;
83
84    textureStore(ambient_occlusion, pixel_coordinates, vec4<f32>(denoised_visibility, 0.0, 0.0, 0.0));
85}