Merge pull request #280 from Unity-Technologies/Object-space-normal-improvement

HDRednerPipeline: compute normalOS in WS with surface gradient

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

         // /We need to decompress the normal ourselve here as UnpackNormalRGB will return a surface gradient
         float3 normalOS = SAMPLE_TEXTURE2D(ADD_IDX(_NormalMapOS), SAMPLER_NORMALMAP_IDX, ADD_IDX(layerTexCoord.base).uv).xyz * 2.0 - 1.0;
         // no need to renormalize normalOS for SurfaceGradientFromPerturbedNormal
-        normalTS = SurfaceGradientFromPerturbedNormal(TransformWorldToObjectDir(input.worldToTangent[2]), normalOS);
+        normalTS = SurfaceGradientFromPerturbedNormal(input.worldToTangent[2], TransformObjectToWorldDir(normalOS));
         #else
         float3 normalOS = UnpackNormalRGB(SAMPLE_TEXTURE2D(ADD_IDX(_NormalMapOS), SAMPLER_NORMALMAP_IDX, ADD_IDX(layerTexCoord.base).uv), 1.0);
         normalTS = TransformObjectToTangent(normalOS, input.worldToTangent);