Some fixes of RTHandleSystem

ScriptableRenderPipeline/Core/CoreRP/Textures/RTHandleSystem.cs

             newRT.m_EnableRandomWrite = enableRandomWrite;
             newRT.m_EnableMSAA = enableMSAA;
             newRT.m_Name = name;
+
+            newRT.referenceSize = new Vector2Int(width, height);
+            
             return newRT;
         }
 
                 memoryless,
                 name
             );
+
+            rth.referenceSize = new Vector2Int(width, height);
 
             rth.scaleFactor = scaleFactor;
             return rth;
                 memoryless,
                 name
             );
+
+            rth.referenceSize = new Vector2Int(width, height);
 
             rth.scaleFunc = scaleFunc;
             return rth;

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Camera/HDCamera.cs

 
         HDAdditionalCameraData m_AdditionalCameraData;
 
-        BufferedRTHandleSystem m_HistoryRTSystem = null;
+        BufferedRTHandleSystem m_HistoryRTSystem = new BufferedRTHandleSystem();
 
         public HDCamera(Camera cam)
         {
             // Unfortunately sometime (like in the HDCameraEditor) HDUtils.hdrpSettings can be null because of scripts that change the current pipeline...
             m_msaaSamples = HDUtils.hdrpSettings != null ? HDUtils.hdrpSettings.msaaSampleCount : MSAASamples.None;
             RTHandles.SetReferenceSize(m_ActualWidth, m_ActualHeight, frameSettings.enableMSAA, m_msaaSamples);
-            if (m_HistoryRTSystem != null)
-            {
-                m_HistoryRTSystem.SetReferenceSize(m_ActualWidth, m_ActualHeight, frameSettings.enableMSAA, m_msaaSamples);
-                m_HistoryRTSystem.Swap();
-            }
+            m_HistoryRTSystem.SetReferenceSize(m_ActualWidth, m_ActualHeight, frameSettings.enableMSAA, m_msaaSamples);
+            m_HistoryRTSystem.Swap();
 
             int maxWidth = RTHandles.maxWidth;
             int maxHeight = RTHandles.maxHeight;
 
         public RTHandleSystem.RTHandle GetPreviousFrameRT(int id)
         {
-            return m_HistoryRTSystem != null
-                ? m_HistoryRTSystem.GetFrameRT(id, 1)
-                : null;
+            return m_HistoryRTSystem.GetFrameRT(id, 1);
-            return m_HistoryRTSystem != null
-                ? m_HistoryRTSystem.GetFrameRT(id, 0)
-                : null;
+            return m_HistoryRTSystem.GetFrameRT(id, 0);
-            if (m_HistoryRTSystem == null)
-                m_HistoryRTSystem = new BufferedRTHandleSystem();
             m_HistoryRTSystem.AllocBuffer(id, (rts, i) => allocator(camera.name, i, rts), 2);
             return m_HistoryRTSystem.GetFrameRT(id, 0);
         }
-            if (m_HistoryRTSystem != null)
-                m_HistoryRTSystem.ReleaseAll();
+            m_HistoryRTSystem.ReleaseAll();
         }
     }
 }

ScriptableRenderPipeline/HDRenderPipeline/HDRP/RenderPipelineResources/BufferPyramid.cs

         public int GetPyramidLodCount(Vector2Int size)
         {
             var minSize = Mathf.Min(size.x, size.y);
-            return Mathf.FloorToInt(Mathf.Log(minSize, 2f));
+            return Mathf.Max(0, Mathf.FloorToInt(Mathf.Log(minSize, 2f)));
         }
 
         Vector2Int CalculatePyramidMipSize(Vector2Int baseMipSize, int mipIndex)
                 GetPyramidLodCount(targetDepthTexture.referenceSize),
                 GetPyramidLodCount(new Vector2Int(hdCamera.actualWidth, hdCamera.actualHeight))
             );
+            if (lodCount == 0)
+            {
+                Debug.LogWarning("The target for the pyramid buffer has an invalid size. Skipping DepthPyramid calculation.");
+                return;
+            }
+
             UpdatePyramidMips(hdCamera, targetDepthTexture.rt.format, m_DepthPyramidMips, lodCount);
 
             Vector2 scale = GetPyramidToScreenScale(hdCamera, targetDepthTexture);
                 GetPyramidLodCount(targetColorTexture.referenceSize),
                 GetPyramidLodCount(new Vector2Int(hdCamera.actualWidth, hdCamera.actualHeight))
             );
+            if (lodCount == 0)
+            {
+                Debug.LogWarning("The target for the pyramid buffer has an invalid size. Skipping ColorPyramid calculation.");
+                return;
+            }
+
             UpdatePyramidMips(hdCamera, targetColorTexture.rt.format, m_ColorPyramidMips, lodCount);
 
             Vector2 scale = GetPyramidToScreenScale(hdCamera, targetColorTexture);