Rename EnableDBuffer to EnableDecals + Fix issue with MAOS

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

                         if ((maskmapMetal.floatValue == 0.0f) && (maskmapAO.floatValue == 0.0f) && (maskmapSmoothness.floatValue == 0.0f))
                             maskmapSmoothness.floatValue = 1.0f;
 
+                        maskBlendFlags = 0; // Re-init the mask
+
                         if (maskmapMetal.floatValue == 1.0f)
                             maskBlendFlags |= Decal.MaskBlendFlags.Metal;
                         if (maskmapAO.floatValue == 1.0f)
                     }
+                    else // if perChannelMask is not enabled, force to have smoothness
+                    {
+                        maskBlendFlags = Decal.MaskBlendFlags.Smoothness;
+                    }
+
                 m_MaterialEditor.ShaderProperty(decalBlend, Styles.decalBlendText);
                 m_MaterialEditor.ShaderProperty(decalMeshDepthBias, Styles.MeshDecalDepthBiasText);
                 EditorGUI.indentLevel--;

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

 {
     public class DBufferManager : MRTBufferManager
     {
-        public bool enableDBuffer { get; set; }
+        public bool enableDecals { get; set; }
 
         RTHandleSystem.RTHandle m_HTile;
 
         {
             if (hdCamera.frameSettings.enableDecals)
             {
-                cmd.SetGlobalInt(HDShaderIDs._EnableDBuffer, enableDBuffer ? 1 : 0);
+                cmd.SetGlobalInt(HDShaderIDs._EnableDecals, enableDecals ? 1 : 0);
-                cmd.SetGlobalInt(HDShaderIDs._EnableDBuffer, 0);
+                cmd.SetGlobalInt(HDShaderIDs._EnableDecals, 0);
                 // We still bind black textures to make sure that something is bound (can be a problem on some platforms)
                 for (int i = 0; i < m_BufferCount; ++i)
                 {

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

 {
     ZERO_INITIALIZE(DecalSurfaceData, surfaceData);
     surfaceData.baseColor = inDBuffer0;
-    surfaceData.normalWS.xyz = inDBuffer1.xyz * 2.0f - 1.0f;
+    surfaceData.normalWS.xyz = inDBuffer1.xyz * 2.0 - 1.0;
     surfaceData.normalWS.w = inDBuffer1.w;
     surfaceData.mask = inDBuffer2;
 #ifdef _DECALS_4RT

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

 
 void AddDecalContribution(PositionInputs posInput, inout SurfaceData surfaceData, inout float alpha)
 {
-    if (_EnableDBuffer)
+    if (_EnableDecals)
-        DecalSurfaceData decalSurfaceData;
         int mask = 0;
         // the code in the macros, gets moved inside the conditionals by the compiler
         FETCH_DBUFFER(DBuffer, _DBufferTexture, posInput.positionSS);
 #else
         mask = UnpackByte(LOAD_TEXTURE2D(_DecalHTileTexture, posInput.positionSS / 8).r);
 #endif
+        DecalSurfaceData decalSurfaceData;
         DECODE_FROM_DBUFFER(DBuffer, decalSurfaceData);
         // using alpha compositing https://developer.nvidia.com/gpugems/GPUGems3/gpugems3_ch23.html
         if (mask & DBUFFERHTILEBIT_DIFFUSE)
         {
             surfaceData.normalWS.xyz = normalize(surfaceData.normalWS.xyz * decalSurfaceData.normalWS.w + decalSurfaceData.normalWS.xyz);
         }
+
         if (mask & DBUFFERHTILEBIT_MASK)
         {
 #ifdef _DECALS_4RT // only smoothness in 3RT mode

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

 #ifdef SHADER_VARIABLES_INCLUDE_CB
-    uint    _EnableDBuffer;
+    uint    _EnableDecals;
     float2  _DecalAtlasResolution;
 #else
 #endif

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

 
                     m_ReflectionProbeCullResults.Cull();
 
-                    m_DbufferManager.enableDBuffer = false;
+                    m_DbufferManager.enableDecals = false;
-                            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
+                            m_DbufferManager.enableDecals = 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
                 }
             }
             // If we enable DBuffer, we need a full depth prepass
-            else if (hdCamera.frameSettings.enableDepthPrepassWithDeferredRendering || m_DbufferManager.enableDBuffer)
+            else if (hdCamera.frameSettings.enableDepthPrepassWithDeferredRendering || m_DbufferManager.enableDecals)
-                using (new ProfilingSample(cmd, m_DbufferManager.enableDBuffer ? "Depth Prepass (deferred) force by DBuffer" : "Depth Prepass (deferred)", CustomSamplerId.DepthPrepass.GetSampler()))
+                using (new ProfilingSample(cmd, m_DbufferManager.enableDecals ? "Depth Prepass (deferred) force by Decals" : "Depth Prepass (deferred)", CustomSamplerId.DepthPrepass.GetSampler()))
                 {
                     cmd.DisableShaderKeyword("WRITE_NORMAL_BUFFER"); // Note: This only disable the output of normal buffer for Lit shader, not the other shader that don't use multicompile
 

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

         public static readonly int _CameraFilteringBuffer          = Shader.PropertyToID("_CameraFilteringTexture");
         public static readonly int _IrradianceSource               = Shader.PropertyToID("_IrradianceSource");
 
-        public static readonly int _EnableDBuffer = Shader.PropertyToID("_EnableDBuffer");
+        public static readonly int _EnableDecals = Shader.PropertyToID("_EnableDecals");
         public static readonly int _DecalAtlasResolution = Shader.PropertyToID("_DecalAtlasResolution");
 
         public static readonly int[] _GBufferTexture =