Solari fixes (#21747)

* Fix overflow/nans in BRDF evaluation
* Reduce jacobian rejection threshold to prevent light leaks (more
aggressive cutoff now)

Author: JMS55

crates/bevy_solari/src/pathtracer/pathtracer.wgsl

@@ -104,7 +104,7 @@ fn importance_sample_next_bounce(wo: vec3<f32>, ray_hit: ResolvedRayHitFull, rng
     if is_perfectly_specular {
         return NextBounce(reflect(-wo, ray_hit.world_normal), 1.0, true);
     }
-    let diffuse_weight = mix(mix(0.4f, 0.9f, ray_hit.material.perceptual_roughness), 0.f, ray_hit.material.metallic);
+    let diffuse_weight = mix(mix(0.4, 0.9, ray_hit.material.perceptual_roughness), 0.0, ray_hit.material.metallic);
     let specular_weight = 1.0 - diffuse_weight;
 
     let TBN = calculate_tbn_mikktspace(ray_hit.world_normal, ray_hit.world_tangent);
@@ -133,7 +133,7 @@ fn importance_sample_next_bounce(wo: vec3<f32>, ray_hit: ResolvedRayHitFull, rng
 }
 
 fn brdf_pdf(wo: vec3<f32>, wi: vec3<f32>, ray_hit: ResolvedRayHitFull) -> f32 {
-    let diffuse_weight = mix(mix(0.4f, 0.9f, ray_hit.material.roughness), 0.f, ray_hit.material.metallic);
+    let diffuse_weight = mix(mix(0.4, 0.9, ray_hit.material.roughness), 0.0, ray_hit.material.metallic);
     let specular_weight = 1.0 - diffuse_weight;
 
     let TBN = calculate_tbn_mikktspace(ray_hit.world_normal, ray_hit.world_tangent);

crates/bevy_solari/src/realtime/gbuffer_utils.wgsl

@@ -18,11 +18,12 @@ fn gpixel_resolve(gpixel: vec4<u32>, depth: f32, pixel_id: vec2<u32>, view_size:
 
     let base_rough = unpack4x8unorm(gpixel.r);
     let base_color = pow(base_rough.rgb, vec3(2.2));
-    let perceptual_roughness = base_rough.a;
-    let roughness = clamp(perceptual_roughness * perceptual_roughness, 0.001, 1.0);
+    // Clamp roughness to prevent NaNs
+    let perceptual_roughness = clamp(base_rough.a, 0.0316227766, 1.0); // Clamp roughness to 0.001
+    let roughness = perceptual_roughness * perceptual_roughness;
     let props = unpack4x8unorm(gpixel.b);
     let reflectance = vec3(props.r);
-    let metallic = props.g;
+    let metallic = saturate(props.g); // TODO: Not sure why saturate is needed here to prevent NaNs
     let emissive = rgb9e5_to_vec3_(gpixel.g);
     let material = ResolvedMaterial(base_color, emissive, reflectance, perceptual_roughness, roughness, metallic);
 

crates/bevy_solari/src/realtime/restir_gi.wgsl

@@ -274,7 +274,7 @@ fn merge_reservoirs(
     );
 
     // Don't merge samples with huge jacobians, as it explodes the variance
-    if canonical_target_function_other_sample_jacobian > 2.0 {
+    if canonical_target_function_other_sample_jacobian > 1.2 {
         return ReservoirMergeResult(canonical_reservoir, canonical_sample_radiance);
     }
 

crates/bevy_solari/src/scene/raytracing_scene_bindings.wgsl

@@ -142,7 +142,10 @@ fn resolve_material(material: Material, uv: vec2<f32>) -> ResolvedMaterial {
         m.perceptual_roughness *= metallic_roughness.g;
         m.metallic *= metallic_roughness.b;
     }
-    m.roughness = clamp(m.perceptual_roughness * m.perceptual_roughness, 0.001, 1.0);
+
+    // Clamp roughness to prevent NaNs
+    m.perceptual_roughness = clamp(m.perceptual_roughness, 0.0316227766, 1.0); // Clamp roughness to 0.001
+    m.roughness = m.perceptual_roughness * m.perceptual_roughness;
 
     return m;
 }