Fix normal filtering, which fixes both IBL and direct lighting flashing

3 files changed, 17 insertions, 19 deletions

diff --git a/brdf.cginc b/brdf.cginc
index 45d350e..94e7858 100755
--- a/brdf.cginc
+++ b/brdf.cginc
@@ -42,7 +42,7 @@ float3 F_Schlick(float LoH, float3 f0, float f90) {
 // The `max(1e-4, _)` and `min(4096, _)` are hand picked to minimize the issue
 // of bloom making specular highlights flash as the camera moves.
 float D_GGX(float roughness, float NoH) {
-  float r2 = max(1e-4, roughness * roughness);
+  float r2 = roughness * roughness;
   float NoH2 = NoH * NoH;
   float NoH4 = NoH2 * NoH2;
 
@@ -50,7 +50,8 @@ float D_GGX(float roughness, float NoH) {
   float r2_plus_k = r2 + k;
   float denom = NoH4 * r2_plus_k * r2_plus_k;
 
-  return min(4096, r2 / denom);
+  //return min(4096, r2 / denom);
+  return r2 / denom;
 }
 
 // Hammon "PBR Diffuse Lighting for GGX+Smith Microsurfaces"
@@ -144,8 +145,6 @@ float4 brdf(Pbr pbr, LightData data, out BrdfData bd) {
     diffuse += direct_diffuse;
   }
 
-  return float4(specular + diffuse, 1);
-
   // Indirect
 #if !defined(FURNACE_TEST_DIRECT) && (defined(FORWARD_BASE_PASS) || defined(OUTLINES_PASS))
   {
diff --git a/data.cginc b/data.cginc
index cbab2c7..d7883a8 100644
--- a/data.cginc
+++ b/data.cginc
@@ -11,6 +11,7 @@
 
 struct Pbr {
   float4 albedo;
+  float3 geometric_normal;
   float3 normal;
   float3x3 tbn;
   float smoothness;
diff --git a/pbr.cginc b/pbr.cginc
index f3c46a5..33264ce 100755
--- a/pbr.cginc
+++ b/pbr.cginc
@@ -94,31 +94,28 @@ float2 parallax_offset(float2 uv, float3 view_dir_world, float3x3 tbn) {
 }
 #endif  // _PARALLAX_HEIGHTMAP
 
-// Tokuyashi and Kaplanyan 2019 "Improved Geometric Specular Antialiasing"
-float normalFiltering(float3 normal, float perceptual_roughness) {
-  float3 du = ddx(normal);
-  float3 dv = ddy(normal);
+// Tokuyoshi and Kaplanyan 2019 "Improved Geometric Specular Antialiasing"
+float normalFiltering(float3 geometric_normal, float perceptual_roughness) {
+  float3 du = ddx(geometric_normal);
+  float3 dv = ddy(geometric_normal);
 
-  // Boxed equation in section 3.2 "Proposed Error Reduction."
-  float variance = dot(du, du) + dot(dv, dv);
-  float sigma = 0.5f;  // standard deviation of pixel filter kernel in image space
-  float Sigma = sigma * sigma * variance;
-
-  // Equation 1 in section 4.2 "Constraint for Conservative Isotropic Filtering"
+  float variance = _Specular_AA_Variance * (dot(du, du) + dot(dv, dv));
   float roughness = perceptual_roughness * perceptual_roughness;
-  float kappa = 0.18;
-  roughness = roughness + min(2 * Sigma, kappa);
+  float kernel_roughness = min(2.0f * variance, _Specular_AA_Threshold);
+  float square_roughness = saturate(roughness * roughness + kernel_roughness);
 
-  return saturate(sqrt(roughness));
+  return saturate(sqrt(sqrt(square_roughness)));
 }
 
 void propagateSmoothness(inout Pbr pbr) {
-  pbr.smoothness = 1.0f - normalFiltering(pbr.normal, 1.0f - pbr.smoothness);
+  pbr.smoothness = 1.0f - normalFiltering(pbr.geometric_normal, 1.0f - pbr.smoothness);
 
   pbr.roughness_perceptual = clamp(1.0f - pbr.smoothness, MIN_PERCEPTUAL_ROUGHNESS, 1);
   pbr.roughness = clamp(pbr.roughness_perceptual * pbr.roughness_perceptual, MIN_ROUGHNESS, 1);
 #if defined(_CLEARCOAT)
-  pbr.cc_roughness = max(MIN_ROUGHNESS, pbr.cc_roughness * pbr.cc_roughness);
+  pbr.cc_roughness_perceptual = clamp(pbr.cc_roughness_perceptual, MIN_PERCEPTUAL_ROUGHNESS, 1);
+  pbr.cc_roughness_perceptual = normalFiltering(pbr.geometric_normal, pbr.cc_roughness_perceptual);
+  pbr.cc_roughness = max(MIN_ROUGHNESS, pbr.cc_roughness_perceptual * pbr.cc_roughness_perceptual);
 #endif
 }
 
@@ -181,6 +178,7 @@ Pbr getPbr(v2f i) {
   Pbr pbr = (Pbr) 0;
 
   float3 n = i.normal;
+  pbr.geometric_normal = n;
   float3 t = i.tangent.xyz;
   t = normalize(t - n * dot(n, t));  // Gram-Schmidt to avoid skew
   float3 b = normalize(cross(n, t)) * i.tangent.w;