Albedo contribution flag works on transparency

com.unity.render-pipelines.high-definition/HDRP/Material/Decal/Decal.cs

             sRGBFlags = m_sRGBFlags;
         }
     }
-
-    // normalToWorld.m03 - total blend factor
-    // normalToWorld.m13 - diffuse texture index in atlas
-    // normalToWorld.m23 - normal texture index in atlas
-    // normalToWorld.m33 - mask texture index in atlas
+    
+    // normal to world only uses 3x3 for actual matrix so some data is packed in the unused space
+    // blend:
+    // float decalBlend = decalData.normalToWorld[0][3];
+    // albedo contribution on/off:
+    // float albedoContribution = decalData.normalToWorld[1][3];
+    // tiling:
+    // float2 uvScale = float2(decalData.normalToWorld[3][0], decalData.normalToWorld[3][1]);
+    // float2 uvBias = float2(decalData.normalToWorld[3][2], decalData.normalToWorld[3][3]);
     [GenerateHLSL]
     public struct DecalData
     {

com.unity.render-pipelines.high-definition/HDRP/Material/Decal/DecalSystem.cs

                 m_Normal.m_Texture = m_Material.GetTexture("_NormalMap");
                 m_Mask.m_Texture = m_Material.GetTexture("_MaskMap");
                 m_Blend = m_Material.GetFloat("_DecalBlend");
+                m_AlbedoContribution = m_Material.GetFloat("_AlbedoMode");
             }
 
             public DecalSet(Material material)
                         normalToWorldBatch[instanceCount] = m_CachedNormalToWorld[decalIndex];
                         float fadeFactor = Mathf.Clamp((cullDistance - distanceToDecal) / (cullDistance * (1.0f - m_CachedDrawDistances[decalIndex].y)), 0.0f, 1.0f);
                         normalToWorldBatch[instanceCount].m03 = fadeFactor * m_Blend;   // vector3 rotation matrix so bottom row and last column can be used for other data to save space
+                        normalToWorldBatch[instanceCount].m13 = m_AlbedoContribution;
                         normalToWorldBatch[instanceCount].SetRow(3, m_CachedUVScaleBias[decalIndex]);
 
                         // clustered forward data
             private Vector4[] m_CachedUVScaleBias = new Vector4[kDecalBlockSize]; // xy - scale, zw bias
             private Material m_Material;
             private float m_Blend = 0;
+            private float m_AlbedoContribution = 0;
 
             TextureScaleBias m_Diffuse = new TextureScaleBias();
             TextureScaleBias m_Normal = new TextureScaleBias();

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

 
                 if((decalData.diffuseScaleBias.x > 0) && (decalData.diffuseScaleBias.y > 0))
                 {
-                    ApplyBlendDiffuse(DBuffer0, mask, sampleDiffuse, DBUFFERHTILEBIT_DIFFUSE, decalBlend, lodDiffuse);
-                    alpha = alpha < decalBlend ? decalBlend : alpha;    // use decal alpha if it is higher than transparent alpha
+					ApplyBlendDiffuse(DBuffer0, mask, sampleDiffuse, DBUFFERHTILEBIT_DIFFUSE, decalBlend, lodDiffuse);						
+					float albedoContribution = decalData.normalToWorld[1][3];
+					if (albedoContribution == 0.0f)
+					{
+						mask = 0;	// diffuse will not get modified						
+					}
+					alpha = alpha < decalBlend ? decalBlend : alpha;    // use decal alpha if it is higher than transparent alpha
                 }
 
                 if ((decalData.normalScaleBias.x > 0) && (decalData.normalScaleBias.y > 0))

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

                         if (hdCamera.frameSettings.enableDBuffer)
                         {
                             DecalSystem.instance.EndCull();
-                            //m_DbufferManager.vsibleDecalCount = DecalSystem.m_DecalsVisibleThisFrame;
-                            m_DbufferManager.EnableDBUffer = true;
+                            m_DbufferManager.EnableDBUffer = true;              // mesh decals are renderers managed by c++ runtime and we have no way to query if any are visible, so set to true
                             DecalSystem.instance.UpdateCachedMaterialData();    // textures, alpha or fade distances could've changed
                             DecalSystem.instance.CreateDrawData();              // prepare data is separate from draw
                             DecalSystem.instance.UpdateTextureAtlas(cmd);       // as this is only used for transparent pass, would've been nice not to have to do this if no transparent renderers are visible, needs to happen after CreateDrawData
                     ClearBuffers(hdCamera, cmd);
 
                     // TODO: Add stereo occlusion mask
-
-                    bool forcePrepassForDecals = m_DbufferManager.EnableDBUffer;
-                    RenderDepthPrepass(m_CullResults, hdCamera, renderContext, cmd, forcePrepassForDecals);
+                    RenderDepthPrepass(m_CullResults, hdCamera, renderContext, cmd, m_DbufferManager.EnableDBUffer);
 
                     // This will bind the depth buffer if needed for DBuffer)
                     RenderDBuffer(hdCamera, cmd, renderContext, m_CullResults);
                 else
                 {
                     HDUtils.SetRenderTarget(cmd, hdCamera, m_CameraColorBuffer, m_CameraDepthStencilBuffer);
-                    //if ((hdCamera.frameSettings.enableDBuffer) && (DecalSystem.m_DecalsVisibleThisFrame > 0)) // enable d-buffer flag value is being interpreted more like enable decals in general now that we have clustered
-                    if (hdCamera.frameSettings.enableDBuffer)
+                    if ((hdCamera.frameSettings.enableDBuffer) && (DecalSystem.m_DecalsVisibleThisFrame > 0)) // enable d-buffer flag value is being interpreted more like enable decals in general now that we have clustered                    
                     {
                         DecalSystem.instance.SetAtlas(cmd); // for clustered decals
                     }

com.unity.render-pipelines.high-definition/HDRP/RenderPipelineResources/DefaultHDMaterial.mat

 Material:
   serializedVersion: 6
   m_ObjectHideFlags: 0
-  m_PrefabParentObject: {fileID: 0}
+  m_CorrespondingSourceObject: {fileID: 0}
   m_PrefabInternal: {fileID: 0}
   m_Name: DefaultHDMaterial
   m_Shader: {fileID: 4800000, guid: 6e4ae4064600d784cac1e41a9e6f2e59, type: 3}
     - _EnableBlendModeAccurateLighting: 1
     - _EnableBlendModePreserveSpecularLighting: 1
     - _EnableFogOnTransparent: 1
+    - _EnableGeometricSpecularAA: 0
     - _EnableMotionVectorForVertexAnimation: 0
     - _EnablePerPixelDisplacement: 0
     - _EnableSpecularOcclusion: 0
     - _GlossMapScale: 1
     - _Glossiness: 0.5
     - _GlossyReflections: 1
+    - _HdrpVersion: 1
     - _HeightAmplitude: 0.01
     - _HeightCenter: 0.5
     - _HeightMapParametrization: 1
     - _Parallax: 0.02
     - _PreRefractionPass: 0
     - _RefractionMode: 0
+    - _RefractionModel: 0
+    - _SSRefractionProjectionModel: 0
     - _SSSAndTransmissionType: 0
     - _ShiverDirectionality: 0.5
     - _ShiverDrag: 0.2
     - _SmoothnessTextureChannel: 0
+    - _SpecularAAScreenSpaceVariance: 0.1
+    - _SpecularAAThreshold: 0.2
     - _SpecularHighlights: 1
     - _SrcBlend: 1
     - _StencilRef: 2
     - _ZTestModeDistortion: 8
     - _ZWrite: 1
     m_Colors:
-    - _BaseColor: {r: 0.72794116, g: 0.72794116, b: 0.72794116, a: 1}
-    - _Color: {r: 0.72794116, g: 0.72794116, b: 0.72794116, a: 1}
+    - _BaseColor: {r: 0.16078432, g: 0.16078432, b: 0.16078432, a: 1}
+    - _Color: {r: 0.16078427, g: 0.16078427, b: 0.16078427, a: 1}
-    - _EmissionColor: {r: 0, g: 0, b: 0, a: 1}
+    - _EmissionColor: {r: 1, g: 1, b: 1, a: 1}
     - _EmissiveColor: {r: 0, g: 0, b: 0, a: 1}
     - _InvPrimScale: {r: 1, g: 1, b: 0, a: 0}
     - _IridescenceThicknessRemap: {r: 0, g: 1, b: 0, a: 0}