Merge pull request #234 from EvgeniiG/master

Fix cookies and shadows not properly affecting transmission

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Lit.hlsl

 // SSS parameters
 #define SSS_N_PROFILES      8
 #define SSS_UNIT_CONVERSION (1.0 / 300.0)                  // From 1/3 centimeters to meters
-#define SSS_LOW_THICKNESS   0.005                          // 5 mm
+#define SSS_LOW_THICKNESS   0.002                          // 2 mm
 
 uint   _EnableSSS;                                         // Globally toggles subsurface scattering on/off
 uint   _TransmissionFlags;                                 // 1 bit/profile; 0 = inf. thick, 1 = supports transmission
         bsdfData.diffuseColor = baseColor;
         // TODO take from subsurfaceProfile
         bsdfData.fresnel0 = 0.04; /* 0.028 ? */
-        bsdfData.subsurfaceProfile = (SSS_N_PROFILES - 1) * inGBuffer2.a + 0.1; // Need to bias for integers to round trip through the G-buffer
+        bsdfData.subsurfaceProfile = (SSS_N_PROFILES - 0.9) * inGBuffer2.a; // Need to bias for integers to round trip through the G-buffer
         // Make the Std. Dev. of 1 correspond to the effective radius of 1 cm (three-sigma rule).
         bsdfData.subsurfaceRadius  = SSS_UNIT_CONVERSION * inGBuffer2.r + 0.0001;
         bsdfData.thickness         = SSS_UNIT_CONVERSION * (_ThicknessRemaps[bsdfData.subsurfaceProfile][0] +
     float4 cookie    = float4(1.0, 1.0, 1.0, 1.0);
     float  shadow    = 1;
 
-    [branch] if (lightData.shadowIndex >= 0 && illuminance > 0.0)
+    [branch] if (lightData.shadowIndex >= 0)
     {
 #ifdef SHADOWS_USE_SHADOWCTXT
         shadow = GetDirectionalShadowAttenuation(lightLoopContext.shadowContext, positionWS, lightData.shadowIndex, L, posInput.unPositionSS);
         illuminance *= shadow;
     }
 
-    [branch] if (lightData.cookieIndex >= 0 && illuminance > 0.0)
+    [branch] if (lightData.cookieIndex >= 0)
     {
         float3 lightToSurface = positionWS - lightData.positionWS;
 
     {
         // Reverse the normal.
         illuminance  = saturate(dot(-bsdfData.normalWS, L));
+        // For low thickness, we can reuse the shadowing status for the back of the object.
         shadow       = (bsdfData.thickness <= SSS_LOW_THICKNESS) ? shadow : 1;
         illuminance *= shadow * cookie.a;
 
     //    illuminance *= SampleIES(lightLoopContext, lightData.IESIndex, sphericalCoord, 0).r;
     //}
 
-    [branch] if (lightData.shadowIndex >= 0 && illuminance > 0.0)
+    [branch] if (lightData.shadowIndex >= 0)
     {
         float3 offset = float3(0.0, 0.0, 0.0); // GetShadowPosOffset(nDotL, normal);
 #ifdef SHADOWS_USE_SHADOWCTXT
         illuminance *= shadow;
     }
 
-    [branch] if (lightData.cookieIndex >= 0 && illuminance > 0.0)
+    [branch] if (lightData.cookieIndex >= 0)
     {
         float3x3 lightToWorld = float3x3(lightData.right, lightData.up, lightData.forward);
 
     {
         // Reverse the normal.
         illuminance  = saturate(dot(-bsdfData.normalWS, L)) * attenuation;
+        // For low thickness, we can reuse the shadowing status for the back of the object.
         shadow       = (bsdfData.thickness <= SSS_LOW_THICKNESS) ? shadow : 1;
         illuminance *= shadow * cookie.a;
 
     float4 cookie    = float4(1.0, 1.0, 1.0, 1.0);
     float shadow = 1;
 
-    [branch] if (lightData.shadowIndex >= 0 && illuminance > 0.0)
+    [branch] if (lightData.shadowIndex >= 0)
     {
 #ifdef SHADOWS_USE_SHADOWCTXT
         shadow = GetDirectionalShadowAttenuation(lightLoopContext.shadowContext, positionWS, lightData.shadowIndex, L, posInput.unPositionSS);
         illuminance *= shadow;
     }
 
-    [branch] if (lightData.cookieIndex >= 0 && illuminance > 0.0)
+    [branch] if (lightData.cookieIndex >= 0)
     {
         // Compute the texture coordinates in [0, 1]^2.
         float2 coord = positionNDC * 0.5 + 0.5;
     {
         // Reverse the normal.
         illuminance  = saturate(dot(-bsdfData.normalWS, L) * clipFactor);
+        // For low thickness, we can reuse the shadowing status for the back of the object.
         shadow       = (bsdfData.thickness <= SSS_LOW_THICKNESS) ? shadow : 1;
         illuminance *= shadow * cookie.a;
 

Assets/ScriptableRenderPipeline/ShaderLibrary/AreaLighting.hlsl

 // N.b.: this function accounts for horizon clipping.
 float DiffuseSphereLightIrradiance(float sinSqSigma, float cosOmega)
 {
-    float sinSqOmega = saturate(1 - cosOmega * cosOmega);
+    float irradiance;
+
+    float sinSqOmega = saturate(1 - cosOmega * cosOmega);
     float cosSqSigma = saturate(1 - sinSqSigma);
     float sinSqGamma = saturate(cosSqSigma / sinSqOmega);
     float cosSqGamma = saturate(1 - sinSqGamma);
     float omega = acos(cosOmega);
     float gamma = asin(sinGamma);
 
-    [branch]
     if (omega < 0 || omega >= HALF_PI + sigma)
     {
         // Full horizon occlusion (case #4).
     float e = sinSqSigma * cosOmega;
-
-    float irradiance;
 
     [branch]
     if (omega < HALF_PI - sigma)
         }
     }
 #else // Ref: Moving Frostbite to Physically Based Rendering, page 47 (2015).
-    float irradiance;
+    float cosSqOmega = cosOmega * cosOmega;
-    if (cosOmega * cosOmega > sinSqSigma)
+    [branch]
+    if (cosSqOmega > sinSqSigma)
-        float a = 1 / sinSqSigma - 1;
-        float w = rsqrt(a);
-        float x = sqrt(a);
-        float y = -x * cosOmega * rsqrt(sinSqOmega);
-        float z = sqrt(sinSqOmega * (1 - y * y));
-        irradiance = INV_PI * ((cosOmega * acos(y) - x * z) * sinSqSigma + atan(z * w));
+        float cotanOmega = cosOmega * rsqrt(1 - cosSqOmega);
+
+        float x = rcp(sinSqSigma) - 1;
+        float y = -cotanOmega * sqrt(x);
+        float z = sqrt(1 - cosSqOmega * rcp(sinSqSigma));
+
+        irradiance = INV_PI * ((cosOmega * acos(y) - z * sqrt(x)) * sinSqSigma + atan(z * rsqrt(x)));
     }
 #endif
     return max(irradiance, 0);