Updated unified buffers logic: removed implicit decay to DEFAULT bufers

3 files changed, 9 insertions, 32 deletions

diff --git a/Graphics/GraphicsEngine/include/BufferBase.hpp b/Graphics/GraphicsEngine/include/BufferBase.hpp
index 0095cabb..9ae6db92 100644
--- a/Graphics/GraphicsEngine/include/BufferBase.hpp
+++ b/Graphics/GraphicsEngine/include/BufferBase.hpp
@@ -41,7 +41,7 @@ namespace Diligent
 {
 
 void ValidateBufferInitData(const BufferDesc& Desc, const BufferData* pBuffData);
-void ValidateBufferDesc(const BufferDesc& Desc);
+void ValidateBufferDesc(const BufferDesc& Desc, const DeviceCaps& deviceCaps);
 
 /// Template class implementing base functionality for a buffer object
 
@@ -80,7 +80,7 @@ public:
         m_pDefaultUAV{nullptr, STDDeleter<BufferViewImplType, TBuffViewObjAllocator>(BuffViewObjAllocator)},
         m_pDefaultSRV{nullptr, STDDeleter<BufferViewImplType, TBuffViewObjAllocator>(BuffViewObjAllocator)}
     {
-        ValidateBufferDesc(this->m_Desc);
+        ValidateBufferDesc(this->m_Desc, pDevice->GetDeviceCaps());
 
         Uint64 DeviceQueuesMask = pDevice->GetCommandQueueMask();
         DEV_CHECK_ERR((this->m_Desc.CommandQueueMask & DeviceQueuesMask) != 0, "No bits in the command queue mask (0x", std::hex, this->m_Desc.CommandQueueMask, ") correspond to one of ", pDevice->GetCommandQueueCount(), " available device command queues");
@@ -134,27 +134,6 @@ protected:
     /// Corrects buffer view description and validates view parameters.
     void CorrectBufferViewDesc(struct BufferViewDesc& ViewDesc);
 
-    void DecayUnifiedBuffer()
-    {
-        VERIFY_EXPR(this->m_Desc.Usage == USAGE_UNIFIED);
-        VERIFY_EXPR(this->m_Desc.CPUAccessFlags != CPU_ACCESS_NONE);
-        if (this->m_Desc.CPUAccessFlags == CPU_ACCESS_WRITE)
-        {
-            this->m_Desc.Usage          = USAGE_DEFAULT;
-            this->m_Desc.CPUAccessFlags = CPU_ACCESS_NONE;
-        }
-        else if (this->m_Desc.CPUAccessFlags == CPU_ACCESS_READ)
-        {
-            this->m_Desc.Usage = USAGE_STAGING;
-        }
-        else
-        {
-            LOG_ERROR_AND_THROW("Unified buffer '", this->m_Desc.Name,
-                                "' cannot be automatically converted to a non-unified buffer "
-                                "because it uses both CPU_ACCESS_WRITE and CPU_ACCESS_READ flags");
-        }
-    }
-
 #ifdef DILIGENT_DEBUG
     TBuffViewObjAllocator& m_dbgBuffViewAllocator;
 #endif
diff --git a/Graphics/GraphicsEngine/interface/GraphicsTypes.h b/Graphics/GraphicsEngine/interface/GraphicsTypes.h
index b87cce67..e83d7e9d 100644
--- a/Graphics/GraphicsEngine/interface/GraphicsTypes.h
+++ b/Graphics/GraphicsEngine/interface/GraphicsTypes.h
@@ -126,15 +126,10 @@ DILIGENT_TYPED_ENUM(USAGE, Uint8)
     /// that can be read and written by GPU and can also be directly accessed by CPU.
     ///
     /// \remarks Unified resources must use at least one of CPU_ACCESS_WRITE or CPU_ACCESS_READ flags.\n
-    /// If it is not possible to create a unified resource, the engine will attempt to create a non-unified
-    /// resource as follows:
-    /// - If CPU_ACCESS_WRITE flag is specified, default-usage resource will be created.
-    /// - If CPU_ACCESS_READ flag is specified, staging resource will be created.
-    /// - If both CPU_ACCESS_WRITE and CPU_ACCESS_READ flags are used, an error will be generated.
-    /// An application must check the actual usage after the resource has been created.
     ///
-    /// Unified buffers are natively supported in Vulkan backend only. In other backends
-    /// they decay into default or staging buffers as described above.
+    ///          An application should check if unified memory is available on the device by quering
+    ///          the device caps (see Diligent::IRenderDevice::GetDeviceCaps and Diligent::GraphicsAdapterInfo).
+    ///          If there is no unified memory, an application should choose another usage type (typically, USAGE_DEFAULT).
     USAGE_UNIFIED,
 
     /// Helper value indicating the total number of elements in the enum
diff --git a/Graphics/GraphicsEngine/src/BufferBase.cpp b/Graphics/GraphicsEngine/src/BufferBase.cpp
index 106fd671..350ffc0f 100644
--- a/Graphics/GraphicsEngine/src/BufferBase.cpp
+++ b/Graphics/GraphicsEngine/src/BufferBase.cpp
@@ -43,7 +43,7 @@ namespace Diligent
     } while (false)
 
 
-void ValidateBufferDesc(const BufferDesc& Desc)
+void ValidateBufferDesc(const BufferDesc& Desc, const DeviceCaps& deviceCaps)
 {
     constexpr Uint32 AllowedBindFlags =
         BIND_VERTEX_BUFFER |
@@ -88,6 +88,9 @@ void ValidateBufferDesc(const BufferDesc& Desc)
             break;
 
         case USAGE_UNIFIED:
+            VERIFY_BUFFER(deviceCaps.AdapterInfo.UnifiedMemory != 0,
+                          "Unified memory is not present on this device. Check the amount of available unified memory "
+                          "in the device caps before creating unified buffers.");
             VERIFY_BUFFER(Desc.CPUAccessFlags != CPU_ACCESS_NONE,
                           "at least one of CPU_ACCESS_WRITE or CPU_ACCESS_READ flags must be specified for a unified buffer.");
             break;