Ambient SH done perpixel until we find a proper solution on how to handle it for ShanderGraph

ScriptableRenderPipeline/LightweightPipeline/Shaders/LightweightLighting.cginc

     half3 emission;
     half  occlusion;
     half  alpha;
-    half3 ambient;
 };
 
 struct SurfaceInput
     outSurfaceData.occlusion = 1.0h;
     outSurfaceData.emission = half3(0.0h, 0.0h, 0.0h);
     outSurfaceData.alpha = 1.0h;
-    outSurfaceData.ambient = half3(0.0h, 0.0h, 0.0h);
 }
 
 half SpecularReflectivity(half3 specular)
     return c;
 }
 
-UnityIndirect LightweightGI(float4 lightmapUV, half3 ambientColor, half3 normalWorld, half3 reflectVec, half occlusion, half perceptualRoughness)
+UnityIndirect LightweightGI(float4 lightmapUV, half3 normalWorld, half3 reflectVec, half occlusion, half perceptualRoughness)
+
-    ambientColor += (DecodeLightmap(UNITY_SAMPLE_TEX2D(unity_Lightmap, lightmapUV.xy)));
+    o.diffuse += (DecodeLightmap(UNITY_SAMPLE_TEX2D(unity_Lightmap, lightmapUV.xy))) * occlusion;
-    ambientColor += SHEvalLinearL0L1(half4(normalWorld, 1.0));
-    ambientColor = max(half3(0.0, 0.0, 0.0), ambientColor);
+    o.diffuse = ShadeSH9(half4(normalWorld, 1.0)) * occlusion;
-
-    o.diffuse = ambientColor * occlusion;
 
 #ifndef _GLOSSYREFLECTIONS_OFF
     Unity_GlossyEnvironmentData g;
 
 half4 LightweightFragmentPBR(half4 lightmapUV, float3 positionWS, half3 normalWS, half3 tangentWS, half3 bitangentWS,
     half3 viewDirectionWS, half fogFactor, half3 albedo, half metallic, half3 specular, half smoothness,
-    half3 normalTS, half ambientOcclusion, half3 emission, half alpha, half3 ambient)
+    half3 normalTS, half ambientOcclusion, half3 emission, half alpha)
 {
     BRDFData brdfData;
     InitializeBRDFData(albedo, metallic, specular, smoothness, alpha, brdfData);
 
     half3 reflectVec = reflect(-viewDirectionWS, normalWS);
     half roughness2 = brdfData.roughness * brdfData.roughness;
-    UnityIndirect indirectLight = LightweightGI(lightmapUV, ambient, normalWS, reflectVec, ambientOcclusion, brdfData.perceptualRoughness);
+    UnityIndirect indirectLight = LightweightGI(lightmapUV, normalWS, reflectVec, ambientOcclusion, brdfData.perceptualRoughness);
 
     // PBS
     half fresnelTerm = Pow4(1.0 - saturate(dot(normalWS, viewDirectionWS)));

ScriptableRenderPipeline/LightweightPipeline/Shaders/LightweightPassLit.cginc

     outSurfaceData.emission = EmissionLW(uv);
     outSurfaceData.emission += IN.fogFactorAndVertexLight.yzw;
     outSurfaceData.alpha = Alpha(albedoAlpha.a);
-
-#if LIGHTMAP_ON
-    outSurfaceData.ambient = half4(0.0h, 0.0h, 0.0h, 0.0h);
-#else
-    outSurfaceData.ambient = half4(IN.ambientOrLightmapUV);
-#endif
 }
 
 void InitializeSurfaceInput(LightweightVertexOutput IN, out SurfaceInput outSurfaceInput)
     o.ambientOrLightmapUV.xy = v.lightmapUV * unity_LightmapST.xy + unity_LightmapST.zw;
     // TODO: Dynamic Lightmap
     o.ambientOrLightmapUV.zw = float2(0.0, 0.0);
-#else
-    o.ambientOrLightmapUV = half4(SHEvalLinearL2(half4(normal, 1.0)), 0.0h);
+
+    // TODO: Currently there's no way to pass in ambient contribution to fragmentPBR.
+    // We should allow to create custom ambient computation for things like SH evaluation, lightmap, ambient color etc.
+//#else
+//    o.ambientOrLightmapUV = half4(SHEvalLinearL2(half4(normal, 1.0)), 0.0h);
 #endif
 
     o.fogFactorAndVertexLight.yzw = half3(0.0h, 0.0h, 0.0h);
     SurfaceInput surfaceInput;
     InitializeSurfaceInput(IN, surfaceInput);
 
-    return LightweightFragmentPBR(surfaceInput.lightmapUV, surfaceInput.positionWS, surfaceInput.normalWS, surfaceInput.tangentWS, surfaceInput.bitangentWS, surfaceInput.viewDirectionWS, surfaceInput.fogFactor, surfaceData.albedo, surfaceData.metallic, surfaceData.specular, surfaceData.smoothness, surfaceData.normal, surfaceData.occlusion, surfaceData.emission, surfaceData.alpha, surfaceData.ambient);
+    return LightweightFragmentPBR(surfaceInput.lightmapUV, surfaceInput.positionWS, surfaceInput.normalWS, surfaceInput.tangentWS, surfaceInput.bitangentWS, surfaceInput.viewDirectionWS, surfaceInput.fogFactor, surfaceData.albedo, surfaceData.metallic, surfaceData.specular, surfaceData.smoothness, surfaceData.normal, surfaceData.occlusion, surfaceData.emission, surfaceData.alpha);
 }
 
 half4 LitPassFragmentSimple(LightweightVertexOutput IN) : SV_Target
 #if defined(LIGHTMAP_ON)
     half3 color = DecodeLightmap(UNITY_SAMPLE_TEX2D(unity_Lightmap, IN.ambientOrLightmapUV.xy)) * diffuse;
 #else
-    half3 color = (SHEvalLinearL0L1(half4(normalWorld, 1.0)) + IN.ambientOrLightmapUV.xyz) * diffuse;
+    half3 color = (ShadeSH9(half4(normalWorld, 1.0)) + IN.ambientOrLightmapUV.xyz) * diffuse;
 #endif
 
     LightInput lightInput;