From dc8a6dfb9d78316b8c58c587bc606468377b0fe3 Mon Sep 17 00:00:00 2001
From: yum <yum.food.vr@gmail.com>
Date: Sat, 4 Oct 2025 19:18:47 -0700
Subject: add unlit toggle, adjust IBL

---
 brdf.cginc | 29 +++++++++++++++++++----------
 1 file changed, 19 insertions(+), 10 deletions(-)

(limited to 'brdf.cginc')

diff --git a/brdf.cginc b/brdf.cginc
index 5a24307..d89558c 100644
--- a/brdf.cginc
+++ b/brdf.cginc
@@ -1,6 +1,7 @@
 #ifndef __BRDF_INC
 #define __BRDF_INC
 
+#include "pema99.cginc"
 #include "pbr.cginc"
 #include "lighting.cginc"
 #include "lysenko.cginc"
@@ -184,14 +185,14 @@ float4 brdf(Pbr pbr, LightData data) {
 #if defined(FORWARD_BASE_PASS)
   {
     float remainder = 1.0f;
-    float2 dfg_uv = float2(data.common.NoV, pbr.roughness);
+    float2 dfg_uv = float2(pbr.roughness, data.common.NoV);
 
 #if defined(_CLEARCOAT)
     float cc_f0 = 0.04f;
     float Fcc = F_Schlick(data.common.NoV, cc_f0, 1.0f);
     float3 indirect_specular_cc = Fcc * data.indirect.specular_cc * pbr.cc_strength;
     specular += indirect_specular_cc;
-    remainder *= (1.0f - Fcc * pbr.cc_strength);
+    remainder -= Fcc * pbr.cc_strength;
 #endif
 
 #if defined(_CLOTH_SHEEN)
@@ -201,19 +202,27 @@ float4 brdf(Pbr pbr, LightData data) {
     // Energy conservation for cloth is tricky with IBL.
     // A simple approximation is to use the Fresnel of the sheen layer.
     float Fcl = F_Schlick(data.common.NoV, 0.04, 1.0);
-    remainder *= (1.0f - Fcl * pbr.cl_strength);
+    remainder -= Fcl * pbr.cl_strength;
 #endif
 
     // Standard PBR IBL using split-sum approximation
-    float2 dfg = _DFG_LUT.Sample(bilinear_clamp_s, dfg_uv).rg;
-    float3 f0_spec = lerp(0.04f, pbr.albedo.xyz, pbr.metallic);
+    // Specular lobe
+    float2 dfg;
+    [branch]
+    if (textureExists(_DFG_LUT)) {
+      dfg = _DFG_LUT.SampleLevel(bilinear_clamp_s, dfg_uv, 0).rg;
+    } else {
+      dfg = float2(0, 1);
+    }
+    float3 f0_spec = lerp(f0, pbr.albedo.xyz, pbr.metallic);
     float3 ibl_specular_reflectance = f0_spec * dfg.x + dfg.y;
     float3 indirect_specular = data.indirect.specular * ibl_specular_reflectance;
-    specular += indirect_specular * remainder;
-
-    // For energy conservation with the diffuse term, we use the view-dependent Fresnel.
-    float3 F = F_Schlick(data.common.NoV, f0_spec, 1.0f);
-    remainder *= (1.0f - F);
+    // surface reduction term lifted from here:
+    // UnityStandardBRDF.cginc :: BRDF1_Unity_PBS
+    float surface_reduction = 1.0f / (pbr.roughness * pbr.roughness + 1.0f);
+    const float F = F_Schlick(data.indirect.NoL, f0_spec, f90);
+    specular += surface_reduction * indirect_specular * F;
+    remainder -= F;
     
     // Diffuse is Lambertian, which is pre-integrated into the SH diffuse probe
     float3 indirect_diffuse = pbr.albedo.xyz * data.indirect.diffuse * remainder * (1.0 - pbr.metallic);
-- 
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