more brdf twiddling

1 files changed, 21 insertions, 14 deletions

diff --git a/brdf.cginc b/brdf.cginc
index 804cfe9..70bca86 100644
--- a/brdf.cginc
+++ b/brdf.cginc
@@ -7,17 +7,26 @@
 #include "lysenko.cginc"
 #include "math.cginc"
 
+float pow5(float x) {
+  float x2 = x * x;
+  return x2 * x2 * x;
+}
+
 // Schlick "An Inexpensive BRDF Model for Physically-based Rendering".
 // Equation 24.
 // f0: Reflectance at normal incidence. Typically around 0.04.
 // f90: Reflectance at grazing incidence. Typically around 1.0.
 float F_Schlick(float LoH, float f0, float f90) {
-  float term = 1.0f - LoH;
-  float term2 = term * term;
-  float term5 = term2 * term2 * term;
+  float term5 = pow5(1.0f - LoH);
   return f0 + (f90 - f0) * term5;
 }
 
+float3 F_Schlick(float LoH, float3 f0, float f90) {
+  float term5 = pow5(1.0f - LoH);
+  float3 f90v = float3(f90, f90, f90);
+  return f0 + (f90v - f0) * term5;
+}
+
 // Walter "Microfacet Models for Refraction through Rough Surfaces"
 // Equation 33.
 // In the paper:
@@ -166,7 +175,7 @@ float4 brdf(Pbr pbr, LightData data) {
 
   // Direct
   {
-    float3 remainder = 1.0f;
+    float3 layer_attenuation = 1.0f;
 
 #if defined(_CLEARCOAT)
     float Fcc = F_Schlick(data.direct.LoH, cc_f0, f90);
@@ -177,7 +186,7 @@ float4 brdf(Pbr pbr, LightData data) {
     direct_specular_cc *= cc_energy_comp;
     direct_specular_cc = max(0, direct_specular_cc);
     specular += direct_specular_cc;
-    remainder = saturate(remainder - direct_specular_cc);
+    layer_attenuation *= saturate(1.0f - Fcc * pbr.cc_strength);
 #endif
 
 #if defined(_CLOTH_SHEEN)
@@ -189,24 +198,22 @@ float4 brdf(Pbr pbr, LightData data) {
     float3 direct_specular_cl = DFGcl * data.direct.color * pbr.cl_strength * pbr.cl_color * data.direct.NoL;
     direct_specular_cl = max(0, direct_specular_cl);
     specular += direct_specular_cl;
-    remainder -= direct_specular_cl;
 #endif
 
-    float F = F_Schlick(data.direct.LoH, f0, f90);
+    float3 F = F_Schlick(data.direct.LoH, f0_color, f90);
     float D = D_GGX(pbr.roughness, data.direct.NoH);
     float G = G_GGXSmith(pbr.roughness, data.direct.NoL, data.common.NoV);
 
-    float FDG = F * D * G;
-    FDG = FDG * dfg.x + dfg.y;
-
-    float3 direct_specular = FDG * remainder * data.direct.color * data.direct.NoL * lerp(1.0f, pbr.albedo.xyz, pbr.metallic);
+    float3 direct_specular = (D * G) * F;
+    direct_specular *= data.direct.color * data.direct.NoL;
     direct_specular *= energy_comp;
+    direct_specular *= layer_attenuation;
     direct_specular = max(0, direct_specular);
     specular += direct_specular;
-    remainder = saturate(remainder - direct_specular);
 
     float Fd = Fd_OrenNayar(pbr.roughness, data.common.NoV, data.direct.NoL, data.direct.LoV) / PI;
-    float3 direct_diffuse = Fd * remainder * (1.0f - pbr.metallic) * pbr.albedo.xyz * data.direct.color;
+    float3 direct_diffuse = Fd * (1.0f - pbr.metallic) * pbr.albedo.xyz * data.direct.color;
+    direct_diffuse *= layer_attenuation;
     direct_diffuse = max(0, direct_diffuse);
     diffuse += direct_diffuse;
   }
@@ -239,7 +246,7 @@ float4 brdf(Pbr pbr, LightData data) {
     float3 f0_spec = lerp(f0, pbr.albedo.xyz, pbr.metallic);
     float3 ibl_specular_reflectance = lerp(dfg.xxx, dfg.yyy, f0_spec);
     float3 indirect_specular = data.indirect.specular * ibl_specular_reflectance * energy_comp;
-    const float F = F_Schlick(data.indirect.NoL, f0_spec, f90);
+    const float3 F = F_Schlick(data.indirect.NoL, f0_spec, f90);
     const float3 is_conserved = indirect_specular * F;
 
     specular += is_conserved;