Fixed an issue in vertex lighting.

ScriptableRenderPipeline/LightweightPipeline/Shaders/LightweightLighting.cginc

     half grazingTerm;
 };
 
-half SpecularReflectivity(half3 specular)
+half ReflectivitySpecular(half3 specular)
-    // SM2.0: simplified SpecularStrength
     return specular.r; // Red channel - because most metals are either monocrhome or with redish/yellowish tint
 #else
     return max(max(specular.r, specular.g), specular.b);
-inline void InitializeBRDFData(half3 albedo, half metallic, half3 specular, half smoothness, half alpha, out BRDFData outBRDFData)
+half OneMinusReflectivityMetallic(half metallic)
-#ifdef _SPECULAR_SETUP
-    half reflectivity = SpecularReflectivity(specular);
-
-    outBRDFData.diffuse = albedo * (half3(1.0h, 1.0h, 1.0h) - specular);
-    outBRDFData.specular = specular;
-#else
     // We'll need oneMinusReflectivity, so
     //   1-reflectivity = 1-lerp(dielectricSpec, 1, metallic) = lerp(1-dielectricSpec, 0, metallic)
     // store (1-dielectricSpec) in kDieletricSpec.a, then
-    half oneMinusReflectivity = oneMinusDielectricSpec - metallic * oneMinusDielectricSpec;
+    return oneMinusDielectricSpec - metallic * oneMinusDielectricSpec;
+}
+
+inline void InitializeBRDFData(half3 albedo, half metallic, half3 specular, half smoothness, half alpha, out BRDFData outBRDFData)
+{
+#ifdef _SPECULAR_SETUP
+    half reflectivity = ReflectivitySpecular(specular);
+    half oneMinusReflectivity = 1.0 - reflectivity;
+
+    outBRDFData.diffuse = albedo * (half3(1.0h, 1.0h, 1.0h) - specular);
+    outBRDFData.specular = specular;
+#else
+
+    half oneMinusReflectivity = OneMinusReflectivityMetallic(metallic);
     half reflectivity = 1.0 - oneMinusReflectivity;
 
     outBRDFData.diffuse = albedo * oneMinusReflectivity;
 
 #ifdef _ALPHAPREMULTIPLY_ON
     outBRDFData.diffuse *= alpha;
-    alpha = reflectivity + alpha * (1.0 - reflectivity);
+    alpha = alpha * oneMinusReflectivity + reflectivity;
 #endif
 }
 

ScriptableRenderPipeline/LightweightPipeline/Shaders/LightweightPassLit.cginc

 #endif
 
 #if _VERTEX_LIGHTS
-    diffuseGI += IN.fogFactorAndVertexLight.yzw;
+    #if _SPECULAR_SETUP
+        // monochrome reflectivity for vertex to save ALU. Most metals are redish/yellowish
+        half3 diffuse = surfaceData.albedo * (1.0 - ReflectivitySpecular(surfaceData.specular));
+    #else
+        half3 diffuse = surfaceData.albedo * OneMinusReflectivityMetallic(surfaceData.metallic);
+    #endif
+    diffuseGI += (diffuse * IN.fogFactorAndVertexLight.yzw);
 #endif
 
     float fogFactor = IN.fogFactorAndVertexLight.x;
     half3 lightDirection;
 
 #if defined(LIGHTMAP_ON)
-    half3 color = SampleLightmap(lightmapUV, normalWorld) * diffuse;
+    half3 color = SampleLightmap(lightmapUV, normalWorld);
-    half3 color = EvaluateSHPerPixel(normalWorld, IN.vertexSH) * diffuse;
+    half3 color = EvaluateSHPerPixel(normalWorld, IN.vertexSH);
+
+    color = (color + IN.fogFactorAndVertexLight.yzw) * diffuse;
 
     half shininess = _Shininess * 128.0h;
 
 #endif // _ADDITIONAL_LIGHTS
 
     color += Emission(uv);
-    color += IN.fogFactorAndVertexLight.yzw;
 
     // Computes Fog Factor per vextex
     ApplyFog(color, IN.fogFactorAndVertexLight.x);