Solari: Misc improvements (#21953)

* Search for a spatial neighbor up to 5 times for ReSTIR instead of just
once.
* Bump RAY_T_MIN to 0.001. Prevents artifacts and doesn't really cause
more self intersections.
* Re-calculate world cache cell_size after jittering the query position
to prevent creating extra cells at the wrong LOD for a given position.
* Prevent the unlikely event of something checksumming to 0, which is
reserved for empty cells.

Author: JMS55

crates/bevy_solari/src/realtime/restir_di.wgsl

@@ -179,15 +179,19 @@ fn load_temporal_reservoir_inner(temporal_pixel_id: vec2<u32>, depth: f32, world
 }
 
 fn load_spatial_reservoir(pixel_id: vec2<u32>, depth: f32, world_position: vec3<f32>, world_normal: vec3<f32>, rng: ptr<function, u32>) -> Reservoir {
-    let spatial_pixel_id = get_neighbor_pixel_id(pixel_id, rng);
+    for (var i = 0u; i < 5u; i++) {
+        let spatial_pixel_id = get_neighbor_pixel_id(pixel_id, rng);
 
-    let spatial_depth = textureLoad(depth_buffer, spatial_pixel_id, 0);
-    let spatial_surface = gpixel_resolve(textureLoad(gbuffer, spatial_pixel_id, 0), spatial_depth, spatial_pixel_id, view.main_pass_viewport.zw, view.world_from_clip);
-    if pixel_dissimilar(depth, world_position, spatial_surface.world_position, world_normal, spatial_surface.world_normal, view) {
-        return empty_reservoir();
+        let spatial_depth = textureLoad(depth_buffer, spatial_pixel_id, 0);
+        let spatial_surface = gpixel_resolve(textureLoad(gbuffer, spatial_pixel_id, 0), spatial_depth, spatial_pixel_id, view.main_pass_viewport.zw, view.world_from_clip);
+        if pixel_dissimilar(depth, world_position, spatial_surface.world_position, world_normal, spatial_surface.world_normal, view) {
+            continue;
+        }
+
+        return load_reservoir_b(spatial_pixel_id);
     }
 
-    return load_reservoir_b(spatial_pixel_id);
+    return empty_reservoir();
 }
 
 fn get_neighbor_pixel_id(center_pixel_id: vec2<u32>, rng: ptr<function, u32>) -> vec2<u32> {

crates/bevy_solari/src/realtime/restir_gi.wgsl

@@ -152,21 +152,25 @@ fn load_temporal_reservoir_inner(temporal_pixel_id: vec2<u32>, depth: f32, world
 }
 
 fn load_spatial_reservoir(pixel_id: vec2<u32>, depth: f32, world_position: vec3<f32>, world_normal: vec3<f32>, rng: ptr<function, u32>) -> NeighborInfo {
-    let spatial_pixel_id = get_neighbor_pixel_id(pixel_id, rng);
+    for (var i = 0u; i < 5u; i++) {
+        let spatial_pixel_id = get_neighbor_pixel_id(pixel_id, rng);
 
-    let spatial_depth = textureLoad(depth_buffer, spatial_pixel_id, 0);
-    let spatial_surface = gpixel_resolve(textureLoad(gbuffer, spatial_pixel_id, 0), spatial_depth, spatial_pixel_id, view.main_pass_viewport.zw, view.world_from_clip);
-    let spatial_diffuse_brdf = spatial_surface.material.base_color / PI;
-    if pixel_dissimilar(depth, world_position, spatial_surface.world_position, world_normal, spatial_surface.world_normal, view) {
-        return NeighborInfo(empty_reservoir(), spatial_surface.world_position, spatial_surface.world_normal, spatial_diffuse_brdf);
-    }
+        let spatial_depth = textureLoad(depth_buffer, spatial_pixel_id, 0);
+        let spatial_surface = gpixel_resolve(textureLoad(gbuffer, spatial_pixel_id, 0), spatial_depth, spatial_pixel_id, view.main_pass_viewport.zw, view.world_from_clip);
+        let spatial_diffuse_brdf = spatial_surface.material.base_color / PI;
+        if pixel_dissimilar(depth, world_position, spatial_surface.world_position, world_normal, spatial_surface.world_normal, view) {
+            continue;
+        }
+
+        let spatial_pixel_index = spatial_pixel_id.x + spatial_pixel_id.y * u32(view.main_pass_viewport.z);
+        var spatial_reservoir = gi_reservoirs_b[spatial_pixel_index];
 
-    let spatial_pixel_index = spatial_pixel_id.x + spatial_pixel_id.y * u32(view.main_pass_viewport.z);
-    var spatial_reservoir = gi_reservoirs_b[spatial_pixel_index];
+        spatial_reservoir.radiance *= trace_point_visibility(world_position, spatial_reservoir.sample_point_world_position);
 
-    spatial_reservoir.radiance *= trace_point_visibility(world_position, spatial_reservoir.sample_point_world_position);
+        return NeighborInfo(spatial_reservoir, spatial_surface.world_position, spatial_surface.world_normal, spatial_diffuse_brdf);
+    }
 
-    return NeighborInfo(spatial_reservoir, spatial_surface.world_position, spatial_surface.world_normal, spatial_diffuse_brdf);
+    return NeighborInfo(empty_reservoir(), world_position, world_normal, vec3(0.0));
 }
 
 fn get_neighbor_pixel_id(center_pixel_id: vec2<u32>, rng: ptr<function, u32>) -> vec2<u32> {

crates/bevy_solari/src/realtime/world_cache_query.wgsl

@@ -47,12 +47,13 @@ struct WorldCacheGeometryData {
 
 #ifndef WORLD_CACHE_NON_ATOMIC_LIFE_BUFFER
 fn query_world_cache(world_position: vec3<f32>, world_normal: vec3<f32>, view_position: vec3<f32>, cell_lifetime: u32, rng: ptr<function, u32>) -> vec3<f32> {
-    let cell_size = get_cell_size(world_position, view_position);
+    var cell_size = get_cell_size(world_position, view_position);
 
     // https://tomclabault.github.io/blog/2025/regir, jitter_world_position_tangent_plane
     let TBN = orthonormalize(world_normal);
     let offset = (rand_vec2f(rng) * 2.0 - 1.0) * cell_size * 0.5;
     let jittered_position = world_position + offset.x * TBN[0] + offset.y * TBN[1];
+    cell_size = get_cell_size(jittered_position, view_position);
 
     let world_position_quantized = bitcast<vec3<u32>>(quantize_position(jittered_position, cell_size));
     let world_normal_quantized = bitcast<vec3<u32>>(quantize_normal(world_normal));
@@ -121,7 +122,7 @@ fn compute_checksum(world_position: vec3<u32>, world_normal: vec3<u32>) -> u32 {
     key = iqint_hash(key + world_normal.x);
     key = iqint_hash(key + world_normal.y);
     key = iqint_hash(key + world_normal.z);
-    return key;
+    return max(key, 1u); // 0u is reserved for WORLD_CACHE_EMPTY_CELL
 }
 
 fn pcg_hash(input: u32) -> u32 {

crates/bevy_solari/src/scene/raytracing_scene_bindings.wgsl

@@ -83,7 +83,7 @@ const LIGHT_NOT_PRESENT_THIS_FRAME = 0xFFFFFFFFu;
 @group(0) @binding(10) var<storage> directional_lights: array<DirectionalLight>;
 @group(0) @binding(11) var<storage> previous_frame_light_id_translations: array<u32>;
 
-const RAY_T_MIN = 0.01f;
+const RAY_T_MIN = 0.001f;
 const RAY_T_MAX = 100000.0f;
 
 const RAY_NO_CULL = 0xFFu;