Enabled support for rendering into slices as the runtime supports it now.

Fixed an error in the atlasing logic.

ScriptableRenderPipeline/Core/CoreRP/Shadow/Shadow.cs

                 // shadow atlas layouting
                 CachedEntry ce = m_EntryCache[i];
                 Rect vp = ce.current.viewport;
+                curh = curh >= vp.height ? curh : vp.height;
+                    curh = vp.height;
                 }
                 if( curx + vp.width > xmax || cury + curh > ymax )
                 {
+                    curh = vp.height;
                 }
                 if( curx + vp.width > xmax || cury + curh > ymax || curslice == m_Slices )
                 {
                 ce.current.slice    = curslice;
                 m_EntryCache[i]     = ce;
                 curx += vp.width;
-                curh = curh >= vp.height ? curh : vp.height;
             }
             return true;
         }

ScriptableRenderPipeline/Core/CoreRP/Shadow/ShadowBase.cs

             m_HeightRcp         = 1.0f / initializer.height;
             m_MaxPayloadCount   = initializer.maxPayloadCount;
             m_ShadowSupport     = initializer.shadowSupport;
-
-            if( IsNativeDepth() && m_Slices > 1 )
-            {
-                // TODO: Right now when using any of the SetRendertarget functions we ultimately end up in RenderTextureD3D11.cpp
-                //       SetRenderTargetD3D11Internal. This function sets the correct slice only for RTVs, whereas depth textures only
-                //       support one DSV. So there's currently no way to have individual DSVs per slice to render into (ignoring going through a geometry shader and selecting the slice there).
-                Debug.LogError( "Unity does not allow direct rendering into specific depth slices, yet. Defaulting back to one array slice." );
-                m_Slices = 1;
-            }
         }
 
         protected bool IsNativeDepth()

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Debug/DebugDisplay.cs

                 {
                     children =
                     {
-                        new DebugUI.UIntField { displayName = "Shadow Atlas Index", getter = () => lightingDebugSettings.shadowAtlasIndex, setter = value => lightingDebugSettings.shadowAtlasIndex = value, min = () => 0u, max = () => (uint)(RenderPipelineManager.currentPipeline as HDRenderPipeline).GetShadowAtlasCount() - 1u }
+                        new DebugUI.UIntField { displayName = "Shadow Atlas Index", getter = () => lightingDebugSettings.shadowAtlasIndex, setter = value => lightingDebugSettings.shadowAtlasIndex = value, min = () => 0u, max = () => (uint)(RenderPipelineManager.currentPipeline as HDRenderPipeline).GetShadowAtlasCount() - 1u },
+                        new DebugUI.UIntField { displayName = "Shadow Slice Index", getter = () => lightingDebugSettings.shadowSliceIndex, setter = value => lightingDebugSettings.shadowSliceIndex = value, min = () => 0u, max = () => (uint)(RenderPipelineManager.currentPipeline as HDRenderPipeline).GetShadowSliceCount(lightingDebugSettings.shadowAtlasIndex) - 1u }
                     }
                 });
             }

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Debug/LightingDebug.cs

         public bool                 shadowDebugUseSelection = false;
         public uint                 shadowMapIndex = 0;
         public uint                 shadowAtlasIndex = 0;
+        public uint                 shadowSliceIndex = 0;
         public float                shadowMinValue = 0.0f;
         public float                shadowMaxValue = 1.0f;
 

ScriptableRenderPipeline/HDRenderPipeline/HDRP/HDRenderPipeline.cs

 
         public int GetCurrentShadowCount() { return m_LightLoop.GetCurrentShadowCount(); }
         public int GetShadowAtlasCount() { return m_LightLoop.GetShadowAtlasCount(); }
+        public int GetShadowSliceCount(uint atlasIndex) { return m_LightLoop.GetShadowSliceCount(atlasIndex); }
 
         readonly SkyManager m_SkyManager = new SkyManager();
         readonly LightLoop m_LightLoop = new LightLoop();

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Lighting/LightLoop/LightLoop.cs

             EnvironmentAndPunctual = 5,
             EnvironmentAndArea = 6,
             EnvironmentAndAreaAndPunctual = 7,
-			Decal = 8
+            Decal = 8
         };
 
         public const int k_MaxDirectionalLightsOnScreen = 4;
             return (m_ShadowMgr == null) ? 0 : (int)m_ShadowMgr.GetShadowMapCount();
         }
 
+        public int GetShadowSliceCount(uint atlasIndex)
+        {
+            return (m_ShadowMgr == null) ? 0 : (int)m_ShadowMgr.GetShadowMapSliceCount(atlasIndex);
+        }
+
         public void UpdateCullingParameters(ref ScriptableCullingParameters cullingParams)
         {
             m_ShadowMgr.UpdateCullingParameters( ref cullingParams );
                 }
                 else if (lightingDebug.shadowDebugMode == ShadowMapDebugMode.VisualizeAtlas)
                 {
-                    m_ShadowMgr.DisplayShadowMap(cmd, m_DebugShadowMapMaterial, lightingDebug.shadowAtlasIndex, 0, x, y, overlaySize, overlaySize, lightingDebug.shadowMinValue, lightingDebug.shadowMaxValue);
+                    m_ShadowMgr.DisplayShadowMap(cmd, m_DebugShadowMapMaterial, lightingDebug.shadowAtlasIndex, lightingDebug.shadowSliceIndex, x, y, overlaySize, overlaySize, lightingDebug.shadowMinValue, lightingDebug.shadowMaxValue);
                     HDUtils.NextOverlayCoord(ref x, ref y, overlaySize, overlaySize, hdCamera.actualWidth);
                 }
             }