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Improve PCSS #22272

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b6ef878
Use PCSS blocker search radius that scales only with cascade resolution
superdump Dec 25, 2025
e39d4e4
Randomly rotate the PCSS blocker search offsets
superdump Dec 25, 2025
3cf1de5
Merge branch 'main' into fix-pcss
superdump Dec 25, 2025
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28 changes: 14 additions & 14 deletions crates/bevy_pbr/src/render/shadow_sampling.wgsl
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Original file line number Diff line number Diff line change
Expand Up @@ -208,6 +208,8 @@ fn sample_shadow_map_jimenez_fourteen(
return sum / 8.0;
}

const PENUMBRA_FILTER_SIZE: vec2<f32> = vec2(128.0f);

// Performs the blocker search portion of percentage-closer soft shadows (PCSS).
// This is the variation used for directional lights.
//
Expand All @@ -222,20 +224,19 @@ fn search_for_blockers_in_shadow_map(
light_local: vec2<f32>,
depth: f32,
array_index: i32,
texel_size: f32,
search_size: f32,
) -> f32 {
let shadow_map_size = vec2<f32>(textureDimensions(view_bindings::directional_shadow_textures));
let uv_offset_scale = search_size / (texel_size * shadow_map_size);

let offset0 = D3D_SAMPLE_POINT_POSITIONS[0] * uv_offset_scale;
let offset1 = D3D_SAMPLE_POINT_POSITIONS[1] * uv_offset_scale;
let offset2 = D3D_SAMPLE_POINT_POSITIONS[2] * uv_offset_scale;
let offset3 = D3D_SAMPLE_POINT_POSITIONS[3] * uv_offset_scale;
let offset4 = D3D_SAMPLE_POINT_POSITIONS[4] * uv_offset_scale;
let offset5 = D3D_SAMPLE_POINT_POSITIONS[5] * uv_offset_scale;
let offset6 = D3D_SAMPLE_POINT_POSITIONS[6] * uv_offset_scale;
let offset7 = D3D_SAMPLE_POINT_POSITIONS[7] * uv_offset_scale;
let rotation_matrix = random_rotation_matrix(light_local * shadow_map_size, false);
let uv_offset_scale = PENUMBRA_FILTER_SIZE / shadow_map_size;

let offset0 = rotation_matrix * D3D_SAMPLE_POINT_POSITIONS[0] * uv_offset_scale;
let offset1 = rotation_matrix * D3D_SAMPLE_POINT_POSITIONS[1] * uv_offset_scale;
let offset2 = rotation_matrix * D3D_SAMPLE_POINT_POSITIONS[2] * uv_offset_scale;
let offset3 = rotation_matrix * D3D_SAMPLE_POINT_POSITIONS[3] * uv_offset_scale;
let offset4 = rotation_matrix * D3D_SAMPLE_POINT_POSITIONS[4] * uv_offset_scale;
let offset5 = rotation_matrix * D3D_SAMPLE_POINT_POSITIONS[5] * uv_offset_scale;
let offset6 = rotation_matrix * D3D_SAMPLE_POINT_POSITIONS[6] * uv_offset_scale;
let offset7 = rotation_matrix * D3D_SAMPLE_POINT_POSITIONS[7] * uv_offset_scale;

var sum = vec2(0.0);
sum += search_for_blockers_in_shadow_map_hardware(light_local + offset0, depth, array_index);
Expand Down Expand Up @@ -289,8 +290,7 @@ fn sample_shadow_map_pcss(
light_size: f32,
) -> f32 {
// Determine the average Z value of the closest blocker.
let z_blocker = search_for_blockers_in_shadow_map(
light_local, depth, array_index, texel_size, light_size);
let z_blocker = search_for_blockers_in_shadow_map(light_local, depth, array_index);

// Don't let the blur size go below 0.5, or shadows will look unacceptably aliased.
let blur_size = max((z_blocker - depth) * light_size / depth, 0.5);
Expand Down