feat: update pathtracer

Author: dylansechet

crates/bevy_solari/src/pathtracer/pathtracer.wgsl

@@ -1,11 +1,11 @@
 enable wgpu_ray_query;
 
 #import bevy_core_pipeline::tonemapping::tonemapping_luminance as luminance
-#import bevy_pbr::pbr_functions::{calculate_tbn_mikktspace, calculate_F0}
+#import bevy_pbr::pbr_functions::calculate_F0_dielectric
 #import bevy_pbr::utils::{rand_f, rand_vec2f}
-#import bevy_render::maths::PI
+#import bevy_render::maths::{PI, orthonormalize}
 #import bevy_render::view::View
-#import bevy_solari::brdf::{evaluate_brdf, evaluate_and_sample_brdf, fresnel}
+#import bevy_solari::brdf::{evaluate_brdf, evaluate_and_sample_brdf, lobe_reflectances}
 #import bevy_solari::sampling::{sample_random_light, random_emissive_light_pdf, ggx_vndf_pdf, power_heuristic}
 #import bevy_solari::scene_bindings::{trace_ray, resolve_ray_hit_full, ResolvedRayHitFull, RAY_T_MIN, RAY_T_MAX, MIRROR_ROUGHNESS_THRESHOLD}
 
@@ -96,23 +96,21 @@ fn pathtrace(@builtin(global_invocation_id) global_id: vec3<u32>) {
 }
 
 fn brdf_pdf(wo: vec3<f32>, wi: vec3<f32>, ray_hit: ResolvedRayHitFull) -> f32 {
-    let NdotV = max(dot(ray_hit.world_normal, wo), 0.0001);
-    let F0 = calculate_F0(ray_hit.material.base_color, ray_hit.material.metallic, vec3(ray_hit.material.reflectance));
-    let df = 1.0 - luminance(fresnel(F0, NdotV));
-
-    let diffuse_weight = mix(df, 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);
+    let TBN = orthonormalize(ray_hit.world_normal);
     let T = TBN[0];
     let B = TBN[1];
     let N = TBN[2];
 
+    let NdotV = max(dot(N, wo), 0.0001);
+    let F0_metal = ray_hit.material.base_color;
+    let F0_dielectric = calculate_F0_dielectric(vec3(ray_hit.material.reflectance));
+    let rho = lobe_reflectances(F0_metal, F0_dielectric, ray_hit.material, NdotV);
+    let specular_weight = luminance(rho.rho_spec) / luminance(rho.rho_spec + rho.rho_diff);
+
     let wo_tangent = vec3(dot(wo, T), dot(wo, B), dot(wo, N));
     let wi_tangent = vec3(dot(wi, T), dot(wi, B), dot(wi, N));
 
     let diffuse_pdf = wi_tangent.z / PI;
     let specular_pdf = ggx_vndf_pdf(wo_tangent, wi_tangent, ray_hit.material.roughness);
-    let pdf = (diffuse_weight * diffuse_pdf) + (specular_weight * specular_pdf);
-    return pdf;
+    return specular_weight * specular_pdf + (1.0 - specular_weight) * diffuse_pdf;
 }