Add opacity parameter for contact shadow

com.unity.render-pipelines.high-definition/HDRP/Editor/Shadows/ContactShadowsEditor.cs

     [VolumeComponentEditor(typeof(ContactShadows))]
     public class ContactShadowsEditor : VolumeComponentEditor
     {
-        public readonly GUIContent contactShadow = new GUIContent("Contact Shadows");
-        public readonly GUIContent contactShadowLength = new GUIContent("Length", "Length of rays used to gather contact shadows in world units.\nZero will disable the feature.");
-        public readonly GUIContent contactShadowDistanceScaleFactor = new GUIContent("Distance Scale Factor", "Contact Shadows are scaled up with distance. Use this parameter to dampen this effect.");
-        public readonly GUIContent contactShadowMaxDistance = new GUIContent("Max Distance", "Distance from the camera in world units at which contact shadows are faded out to zero.");
-        public readonly GUIContent contactShadowFadeDistance = new GUIContent("Fade Distance", "Distance in world units over which the contact shadows are faded out (see Max Distance).");
-        public readonly GUIContent contactShadowSampleCount = new GUIContent("Sample Count", "Number of samples when ray casting.");
-
-
         SerializedDataParameter m_Enable;
         SerializedDataParameter m_Length;
         SerializedDataParameter m_DistanceScaleFactor;
+        SerializedDataParameter m_Opacity;
 
 
         public override void OnEnable()
             m_MaxDistance = Unpack(o.Find(x => x.maxDistance));
             m_FadeDistance = Unpack(o.Find(x => x.fadeDistance));
             m_SampleCount = Unpack(o.Find(x => x.sampleCount));
+            m_Opacity = Unpack(o.Find(x => x.opacity));
         }
 
         public override void OnInspectorGUI()
                     PropertyField(m_MaxDistance, CoreEditorUtils.GetContent("Max Distance|Distance from the camera in world units at which contact shadows are faded out to zero."));
                     PropertyField(m_FadeDistance, CoreEditorUtils.GetContent("Fade Distance|Distance in world units over which the contact shadows fade out (see Max Distance)."));
                     PropertyField(m_SampleCount, CoreEditorUtils.GetContent("Sample Count|Number of samples when ray casting."));
+                    PropertyField(m_Opacity, CoreEditorUtils.GetContent("Opacity|Opacity of the resulting contact shadow."));
                 }
             }
         }

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

                     float contactShadowFadeEnd = m_ContactShadows.maxDistance;
                     float contactShadowOneOverFadeRange = 1.0f / (contactShadowRange);
                     Vector4 contactShadowParams = new Vector4(m_ContactShadows.length, m_ContactShadows.distanceScaleFactor, contactShadowFadeEnd, contactShadowOneOverFadeRange);
-                    cmd.SetComputeVectorParam(screenSpaceShadowComputeShader, HDShaderIDs._DirectionalContactShadowParams, contactShadowParams);
+                    Vector4 contactShadowParams2 = new Vector4(m_ContactShadows.opacity, 0.0f, 0.0f, 0.0f);
+                    cmd.SetComputeVectorParam(screenSpaceShadowComputeShader, HDShaderIDs._ContactShadowParamsParameters, contactShadowParams);
+                    cmd.SetComputeVectorParam(screenSpaceShadowComputeShader, HDShaderIDs._ContactShadowParamsParameters2, contactShadowParams2);
                     cmd.SetComputeIntParam(screenSpaceShadowComputeShader, HDShaderIDs._DirectionalContactShadowSampleCount, m_ContactShadows.sampleCount);
                 }
 

com.unity.render-pipelines.high-definition/HDRP/Lighting/ScreenSpaceShadow.compute

 uint    _DirectionalShadowIndex;
 float4  _DirectionalLightDirection;
 float4  _PunctualLightPosition;
-float4  _ScreenSpaceShadowsParameters;
+float4  _ContactShadowParamsParameters;
+float4  _ContactShadowParamsParameters2;
-#define _ContactShadowLength                _ScreenSpaceShadowsParameters.x
-#define _ContactShadowDistanceScaleFactor   _ScreenSpaceShadowsParameters.y
-#define _ContactShadowFadeEnd               _ScreenSpaceShadowsParameters.z
-#define _ContactShadowFadeOneOverRange      _ScreenSpaceShadowsParameters.w
+#define _ContactShadowLength                _ContactShadowParamsParameters.x
+#define _ContactShadowDistanceScaleFactor   _ContactShadowParamsParameters.y
+#define _ContactShadowFadeEnd               _ContactShadowParamsParameters.z
+#define _ContactShadowFadeOneOverRange      _ContactShadowParamsParameters.w
+#define _ContactShadowOpacity               _ContactShadowParamsParameters2.x
 
 #define DEFERRED_SHADOW_TILE_SIZE 16
 
         contactShadow = 1.0 - result.x * saturate((_ContactShadowFadeEnd - posInput.linearDepth) * _ContactShadowFadeOneOverRange);
     }
 
-    return contactShadow;
+    return lerp(1.0, contactShadow, _ContactShadowOpacity);
 }
 
 [numthreads(DEFERRED_SHADOW_TILE_SIZE, DEFERRED_SHADOW_TILE_SIZE, 1)]
     contactShadow = ComputeContactShadow(posInput, direction);
 
     _DeferredShadowTextureUAV[pixelCoord] = float4(1.0, contactShadow, 1.0, 1.0);
-}
+}

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

         public static readonly int _DeferredShadowTexture = Shader.PropertyToID("_DeferredShadowTexture");
         public static readonly int _DeferredShadowTextureUAV = Shader.PropertyToID("_DeferredShadowTextureUAV");
         public static readonly int _DirectionalShadowIndex = Shader.PropertyToID("_DirectionalShadowIndex");
-        public static readonly int _DirectionalContactShadowParams = Shader.PropertyToID("_ScreenSpaceShadowsParameters");
+        public static readonly int _ContactShadowParamsParameters = Shader.PropertyToID("_ContactShadowParamsParameters");
+        public static readonly int _ContactShadowParamsParameters2 = Shader.PropertyToID("_ContactShadowParamsParameters2");
         public static readonly int _DirectionalContactShadowSampleCount = Shader.PropertyToID("_SampleCount");
         public static readonly int _DirectionalLightDirection = Shader.PropertyToID("_DirectionalLightDirection");
         public static readonly int _PunctualLightPosition = Shader.PropertyToID("_PunctualLightPosition");

com.unity.render-pipelines.high-definition/HDRP/Shadows/ContactShadows.cs

         // Contact shadows
         public BoolParameter                enable = new BoolParameter(false);
         public ClampedFloatParameter        length = new ClampedFloatParameter(0.15f, 0.0f, 1.0f);
+        public ClampedFloatParameter        opacity = new ClampedFloatParameter(1.0f, 0.0f, 1.0f);        
         public ClampedFloatParameter        distanceScaleFactor = new ClampedFloatParameter(0.5f, 0.0f, 1.0f);
         public MinFloatParameter            maxDistance = new MinFloatParameter(50.0f, 0.0f);
         public MinFloatParameter            fadeDistance = new MinFloatParameter(5.0f, 0.0f);