Added a volume to control the indirect light intensity

com.unity.render-pipelines.high-definition/HDRP/Lighting/LightLoop/LightLoop.cs

 
         void PushGlobalParams(HDCamera hdCamera, CommandBuffer cmd)
         {
+            IndirectLightingControl indirectLightVolume = VolumeManager.instance.stack.GetComponent< IndirectLightingControl >();
+            Vector4 indirectLightData = new Vector4(indirectLightVolume.indirectDiffuseIntensity, indirectLightVolume.indirectSpecularIntensity, 0, 0);
+
             using (new ProfilingSample(cmd, "Push Global Parameters", CustomSamplerId.TPPushGlobalParameters.GetSampler()))
             {
                 Camera camera = hdCamera.camera;
 
                 cmd.SetGlobalInt(HDShaderIDs._NumTileClusteredX, GetNumTileClusteredX(hdCamera));
                 cmd.SetGlobalInt(HDShaderIDs._NumTileClusteredY, GetNumTileClusteredY(hdCamera));
+
+                cmd.SetGlobalVector(HDShaderIDs._IndirectLightingMultiplier, (indirectLightVolume != null) ? indirectLightData : Vector4.one);
 
                 if (m_FrameSettings.lightLoopSettings.enableBigTilePrepass)
                     cmd.SetGlobalBuffer(HDShaderIDs.g_vBigTileLightList, s_BigTileLightList);

com.unity.render-pipelines.high-definition/HDRP/Lighting/LightLoop/ShaderVariablesLightLoop.hlsl

     uint _NumTileClusteredX;
     uint _NumTileClusteredY;
 
+    float4 _IndirectLightingMultiplier;
+
     float4x4 _Env2DCaptureVP[MAX_ENV2D_LIGHT];
 
 #else

com.unity.render-pipelines.high-definition/HDRP/Material/Lit/Lit.hlsl

 
     // Apply the albedo to the direct diffuse lighting (only once). The indirect (baked)
     // diffuse lighting has already had the albedo applied in GetBakedDiffuseLighting().
-    diffuseLighting = modifiedDiffuseColor * lighting.direct.diffuse + builtinData.bakeDiffuseLighting;
+    diffuseLighting = modifiedDiffuseColor * lighting.direct.diffuse + builtinData.bakeDiffuseLighting * _IndirectLightingMultiplier.x;
 
     // If refraction is enable we use the transmittanceMask to lerp between current diffuse lighting and refraction value
     // Physically speaking, transmittanceMask should be 1, but for artistic reasons, we let the value vary
 
-    specularLighting = lighting.direct.specular + lighting.indirect.specularReflected;
+    specularLighting = lighting.direct.specular + lighting.indirect.specularReflected * _IndirectLightingMultiplier.y;
     // Rescale the GGX to account for the multiple scattering.
     specularLighting *= 1.0 + bsdfData.fresnel0 * preLightData.energyCompensation;
 

com.unity.render-pipelines.high-definition/HDRP/RenderPipeline/HDStringConstants.cs

         public static readonly int _NumTileFtplY = Shader.PropertyToID("_NumTileFtplY");
         public static readonly int _NumTileClusteredX = Shader.PropertyToID("_NumTileClusteredX");
         public static readonly int _NumTileClusteredY = Shader.PropertyToID("_NumTileClusteredY");
+        
+        public static readonly int _IndirectLightingMultiplier = Shader.PropertyToID("_IndirectLightingMultiplier");
 
         public static readonly int g_isLogBaseBufferEnabled = Shader.PropertyToID("g_isLogBaseBufferEnabled");
         public static readonly int g_vLayeredOffsetsBuffer = Shader.PropertyToID("g_vLayeredOffsetsBuffer");

com.unity.render-pipelines.high-definition/HDRP/Editor/Lighting/IndirectLightingControlEditor.cs

+using System.Collections;
+using UnityEngine;
+using UnityEditor;
+using UnityEditor.Experimental.Rendering;
+
+namespace UnityEngine.Experimental.Rendering.HDPipeline
+{
+    [CanEditMultipleObjects]
+    [VolumeComponentEditor(typeof(IndirectLightingControl))]
+    public class IndirectLightingControlEditor : VolumeComponentEditor
+    {
+        SerializedDataParameter m_IndirectSpecularIntensity;
+        SerializedDataParameter m_IndirectDiffuseIntensity;
+
+        public override void OnEnable()
+        {
+            var o = new PropertyFetcher<IndirectLightingControl>(serializedObject);
+
+            m_IndirectDiffuseIntensity = Unpack(o.Find(x => x.indirectDiffuseIntensity));
+            m_IndirectSpecularIntensity = Unpack(o.Find(x => x.indirectSpecularIntensity));
+        }
+
+        public override void OnInspectorGUI()
+        {
+            PropertyField(m_IndirectSpecularIntensity, CoreEditorUtils.GetContent("Indirect Specular Intensity|Multiplier for the reflected specular light."));
+            PropertyField(m_IndirectDiffuseIntensity, CoreEditorUtils.GetContent("Indirect Diffuse Intensity|Multiplier for the baked diffuse lighting."));
+        }
+    }
+}

com.unity.render-pipelines.high-definition/HDRP/Editor/Lighting/IndirectLightingControlEditor.cs.meta

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com.unity.render-pipelines.high-definition/HDRP/Lighting/IndirectLightingControl.cs

+using System;
+
+namespace UnityEngine.Experimental.Rendering.HDPipeline
+{
+    [Serializable]
+    public class IndirectLightingControl : VolumeComponent
+    {
+        public MinFloatParameter    indirectSpecularIntensity = new MinFloatParameter(1.0f, 0.0f);
+        public MinFloatParameter    indirectDiffuseIntensity = new MinFloatParameter(1.0f, 0.0f);        
+    }
+}

com.unity.render-pipelines.high-definition/HDRP/Lighting/IndirectLightingControl.cs.meta

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