Using DeviceResources

Getting Started

In the basic game loop lesson, we made use of the Direct3D12 Game Visual Studio template which has all the relevant Direct3D code in the Game class including creating the device and swap chain. This makes it easy to teach with, and for the reader to see all the code in one place. This, however, does result in a lot of 'boiler-plate' code in the main Game class which is distracting for the remainder of our tutorial lessons.

There is therefore a "DR" variant of each of the Direct3D Game VS templates in the VS 2019/2022 VSIX package which adds DeviceResources.

If using the Microsoft GDK, then you can use the Direct3D 12 Desktop Game or Direct3D 12 Xbox Game template for any of the remaining tutorial lessons.

The standard Universal Windows Platform app DirectX12App VS templates make use of a similar DeviceResources abstraction.

classDiagram
direction LR
class IDeviceNotify{
   <<Interface>>
   +OnDeviceLost()
   +OnDeviceRestored()
}
class Game{
   +Initialize()
   +Tick()
   -Update()
   -Render()
}
IDeviceNotify <|-- Game
class StepTimer{
   +GetElapsedSeconds() double
   +GetTotalSeconds() double
   +GetFrameCount() uint32_t
   +Tick()
}
Game --o StepTimer : m_timer
class DeviceResources{
    +GetD3DDevice() ID3D12Device
    +GetCommandList() ID3D12GraphicsCommandList
    +GetCommandQueue() ID3D12CommandQueue
    +CreateDeviceResources()
    +CreateWindowSizeDependentResources()
    +Present()
}
Game --o DeviceResources : m_deviceResources

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Creating a new project

Visual Studio 2019 / 2022

• From the drop-down menu, select File and then New -> Project... or on the startup dialog select Create a new project
• Select "Games" on the project types filter. You can optionally type "Win32" or "UWP" in the search box as well.
• Select "Direct3D12 Win32 Game DR" or "Direct3D12 UWP Game DR".
• Select "Next"
• Fill in the "Project name" and "Location" fields as desired.
• Optional: Check "Place solution and project in the same directory" to keep the directory structure as bit flatter.
• Select "Create".

Windows SDK Selection

Using DirectX 12 APIs requires the Windows SDK, so the project wizard will trigger this dialog to select the Windows SDK version to use for UWP templates.

For Win32 projects, the default is to use the latest installed Windows SDK.

Newly Created Project

The newly created project contains the following files:

• Precompiled header files
  • pch.h
  • pch.cpp
• Main application entry-point and classic Windows procedure function or CoreWindow class
  • Main.cpp
• Device resources abstraction
  • DeviceResources.h
  • DeviceResources.cpp
• Timer helper class
  • StepTimer.h
• D3DX12 Utility Header
  • d3dx12.h
• The Game class
  • Game.h
  • Game.cpp

The Win32 version will have the following files as well:

• Resources
  • directx.ico
  • resource.rc
  • settings.manifest

While the UWP version will have:

• Package.appxmanifest
• Name_TemporaryKey.pfx
• Assets
  • logo PNG files

CMake projects

If you prefer to make use of Visual Studio's integrated CMake support or a standalone install of CMake, there are CMakeLists.txt and CMakePresets.json files available for download on directx-vs-templates.

The simplest way to use these is to clone directx-vs-templates, open up PowerShell, change to the directx-vs-templates/VSIX directory, and run the following script which will create a fresh instance of the template set up for CMake development:

.\createcmake.ps1 d3d12game_win32_dr Direct3DGameDR $Env:USERPROFILE\source

If using the Microsoft GDK and wanting to make use of CMake, see the CMakeExample and CMakeGDKExample samples.

COM

The Win32 and UWP templates ensure that the COM library is initialized. This is required for DirectX Tool Kit when using Windows Imaging Component (WIC) functionality. The UWP template also initialize the Windows Runtime, which is required to use Windows.Gaming.Input.

When using the Microsoft GDK 'Game' templates: You'll need to add a call to CoInitializeEx(nullptr, COINIT_MULTITHREADED); to Main.cpp to support WIC.

Running the application

Visual Studio will default to the x64 platform / Debug configuration which builds an x64 (64-bit) application with debugging enabled. The template contains both Debug and Release configurations for both x86 (32-bit) and x64 (x64 native 64-bit) platforms, with UWP also including the ARM platforms.

Press F5 to build and run the application It displays the following window:

Click here for troubleshooting advice

If the base template fails to start, there are a few possibilities:

• First, if your system doesn't have any Direct3D 12 capable device of any feature level, it will fail.
• Second if it runs fine in Release but fails in Debug, then you likely do not have the Graphics Tools Windows feature enabled which is required for the Debug Device.
• Third, if it runs in Debug but not in Release, then you probably don't have a Direct3D 12 capable hardware device and are only able to run the software WARP12 device. Try updating your video drivers and checking the capabilities of your video card.

ARM64: With the ARM64 compiler installed targeting a Windows on ARM64 device such as a Microsoft Surface X, you can build using the ARM64 platform for desktop as well.

Tour of the code

Constructor

The Game class constructor is where you can do first initialization of member variables, as well as where we create the DeviceResources instance.

Game::Game() noexcept(false)
{
    m_deviceResources = std::make_unique<DX::DeviceResources>();
    m_deviceResources->RegisterDeviceNotify(this);
}

The DeviceResources constructor takes a number of defaulted parameters to control backBufferFormat, depthBufferFormat, backBufferCount, minFeatureLevel, and option flags. You can provide specific values to change them as needed.

If doing gamma-correct rendering, you should use DXGI_FORMAT_*_UNORM_SRGB or a supported HDR format for the backBufferFormat. Be sure to update Clear below accordingly to use a linear clear color.

// Use gamma-correct rendering.
m_deviceResources = std::make_unique<DX::DeviceResources>(DXGI_FORMAT_B8G8R8A8_UNORM_SRGB);

If you do not want DeviceResources to create a depth/stencil buffer, you can use DXGI_FORMAT_UNKNOWN for depthBufferFormat. This is useful for 2D only rendering or when doing MSAA which requires handling your own render target and depth buffer with SampleDesc.Count > 1. Be sure to update Clear below to avoid referencing a null depth buffer object.

// Renders only 2D, so no need for a depth buffer.
m_deviceResources = std::make_unique<DX::DeviceResources>(DXGI_FORMAT_B8G8R8A8_UNORM,
    DXGI_FORMAT_UNKNOWN);

The minFeatureLevel defaults to 11 which is the lowest Direct3D Feature Level supported by DirectX 12 drivers. See Microsoft Docs for the definitions of Direct3D hardware feature levels. You can specify a higher hardware level if you want to take a hard dependency on additional capabilities.

m_deviceResources = std::make_unique<DX::DeviceResources>(DXGI_FORMAT_B8G8R8A8_UNORM,
    DXGI_FORMAT_D32_FLOAT, 2, D3D_FEATURE_LEVEL_12_0);

There is one more defaulted parameter for enabling additional features such as such as variable refresh rate or HDR10 output. See DeviceResources for details and usage.

Initialize

When the application first starts, execution is passed to the Initialize method. The TODO here by default leaves the applications StepTimer in the 'variable length' mode. You uncomment the code if you want StepTimer in the 'fixed-step' mode. We'll explain this more once we get to Update.

void Game::Initialize(HWND window, int width, int height)
{
    m_deviceResources->SetWindow(window, width, height);

    m_deviceResources->CreateDeviceResources();
    CreateDeviceDependentResources();

    m_deviceResources->CreateWindowSizeDependentResources();
    CreateWindowSizeDependentResources();

    // TODO: Change the timer settings if you want something other than the default variable timestep mode.
    // e.g. for 60 FPS fixed timestep update logic, call:
    /*
    m_timer.SetFixedTimeStep(true);
    m_timer.SetTargetElapsedSeconds(1.0 / 60);
    */
}

The first Game method Initialize calls is CreateDeviceDependentResources for the creation of objects that depend on the device, but do not care about the size of the rendering window.

void Game::CreateDeviceDependentResources()
{
    auto device = m_deviceResources->GetD3DDevice();

    // TODO: Initialize device dependent objects here (independent of window size).
    device; // This is only here to avoid a warning. You can remove it once you make use of device!
}

The second Game method Initialize calls is CreateWindowSizeDependentResources for creation of objects that depend on the size of the rendering window. Note that this function could be creating these objects for the first time, it could be re-creating already existing objects due to a window-size change, or could be creating 'fresh' objects after a Direct3D device-removed or device-reset case.

void Game::CreateWindowSizeDependentResources()
{
    // TODO: Initialize windows-size dependent objects here.
}

Update

The Update method is intended to handle game-world state modification which is typically driven by time passing, simulation, and/or user-input. By default, Update is called once per 'frame' and can have an arbitrary delta-time. This is called a 'variable-step' mode.

If in the Initialize method above you uncomment the TODO code, then each Update will be for a fixed time-step (1/60th of a second), with Update called as many time in a single 'frame' as needed to keep it up-to-date. This is called a 'fixed-step' mode and potentially be more stable for many kinds of simulations.

void Game::Update(DX::StepTimer const& timer)
{
    PIXBeginEvent(PIX_COLOR_DEFAULT, L"Update");

    float elapsedTime = float(timer.GetElapsedSeconds());

    // TODO: Add your game logic here.
    elapsedTime;

    PIXEndEvent();
}

PIXBeginEvent and PIXEndEvent provide annotations for the Visual Studio Graphics Diagnostics tool (aka VSPIX). To use the latest PIX for Windows, modify the pch.h to include pix3.h instead of pix.h which requires adding a NuGet to your project.

Render

The Render function which should render a single 'frame' of the scene, which starts with a DeviceResources::Prepare and Clear of the render target, and setting the rendering viewport & scissors. It ends with a call to DeviceResources::Present to show the rendered frame.

void Game::Render()
{
    // Don't try to render anything before the first Update.
    if (m_timer.GetFrameCount() == 0)
    {
        return;
    }

    // Prepare the command list to render a new frame.
    m_deviceResources->Prepare();
    Clear();

    auto commandList = m_deviceResources->GetCommandList();
    PIXBeginEvent(commandList, PIX_COLOR_DEFAULT, L"Render");

    // TODO: Add your rendering code here.

    PIXEndEvent(commandList);

    // Show the new frame.
    PIXBeginEvent(m_deviceResources->GetCommandQueue(), PIX_COLOR_DEFAULT, L"Present");
    m_deviceResources->Present();
    PIXEndEvent(m_deviceResources->GetCommandQueue());
}

Prepare

In the non-DR versions of the template, the Clear method would perform the initial command list and allocator reset, as well as transition the render target to the proper state which is required to begin rendering a new frame. In the DeviceResources version, this is handled by the DeviceResources::Prepare method while Clear still performs the actual render target and depth/stencil buffer clear.

Clear

The Clear method defaults to a background color of the classic "Cornflower blue".

void Game::Clear()
{
    auto commandList = m_deviceResources->GetCommandList();

    // Clear the views.
    auto const rtvDescriptor = m_deviceResources->GetRenderTargetView();
    auto const dsvDescriptor = m_deviceResources->GetDepthStencilView();

    commandList->OMSetRenderTargets(1, &rtvDescriptor, FALSE, &dsvDescriptor);
    commandList->ClearRenderTargetView(rtvDescriptor, Colors::CornflowerBlue, 0, nullptr);
    commandList->ClearDepthStencilView(dsvDescriptor, D3D12_CLEAR_FLAG_DEPTH, 1.0f, 0, 0, nullptr);

    // Set the viewport and scissor rect.
    auto const viewport = m_deviceResources->GetScreenViewport();
    auto const scissorRect = m_deviceResources->GetScissorRect();
    commandList->RSSetViewports(1, &viewport);
    commandList->RSSetScissorRects(1, &scissorRect);
}

If you are using gamma-correct rendering with a sRGB or HDR backbuffer format, you need to ensure you are using a linear RGB clear color. DirectXMath colors are defined in sRGB colorspace since they are .NET color constants, so you need to replace ClearRenderTargetView in Clear with:

// Use linear clear color for gamma-correct rendering.
XMVECTORF32 color;
color.v = XMColorSRGBToRGB(Colors::CornflowerBlue);
commandList->ClearRenderTargetView(rtvDescriptor, color, 0, nullptr);

If you chose to not have DeviceResources create a depth/stencil buffer (see the Constructor section), you need to update Clear to avoid reference to a null depth/stencil buffer object.

void Game::Clear()
{
    auto commandList = m_deviceResources->GetCommandList();

    // Clear the views.
    auto const rtvDescriptor = m_deviceResources->GetRenderTargetView();

    commandList->OMSetRenderTargets(1, &rtvDescriptor, FALSE, nullptr);
    commandList->ClearRenderTargetView(rtvDescriptor, Colors::CornflowerBlue, 0, nullptr);

    // Set the viewport and scissor rect.
    auto const viewport = m_deviceResources->GetScreenViewport();
    auto const scissorRect = m_deviceResources->GetScissorRect();
    commandList->RSSetViewports(1, &viewport);
    commandList->RSSetScissorRects(1, &scissorRect);
}

Present

In DirectX 12, the application is responsible for implementing the swapping of the back buffer. The DeviceResources::Present method of inserts a barrier to transition the render target to the present state, closes and executes the command list, presents the current frame, and then advances to the next frame. If needed, any fencing or blocking of rendering due to too many queued frames takes place here as well.

It also checks for "device removed" scenarios.

Events

The template includes a number of message handlers that are called for process state changes: OnActivated, OnDeactivated, OnSuspending, OnResuming, and OnWindowSizeChanged. The UWP version also includes ValidateDevice, and display orientation is provided long with the window size.

For Win32 desktop, the OnSuspending / OnResuming messages are triggered when (a) the window is minimized/unminimized or (b) in reaction to the WM_POWERBROADCAST message. On other platforms, this is driven by Process Lifecycle Management (PLM).

Since we are using ComPtr, most cleanup is automatic when the Game class is destroyed. If Present encounters a device-removed or device-reset, then the application needs to release all Direct3D objects and recreate the device, swapchain, and all Direct3D objects again. Therefore, the TODO in OnDeviceLost should be updated to release your application's Direct3D objects.

void Game::OnDeviceLost()
{
    // TODO: Add Direct3D resource cleanup here

...
}

You will not get "device lost" all that often. In legacy Direct3D 9, you would routinely get a 'device lost' if you just Alt+TAB away from the application because the GPU used to be an 'exclusive' rather than 'shared' resource. The situation where you'd get DXGI_ERROR_DEVICE_RESET is if the driver crashes or the video hardware hangs. You get DXGI_ERROR_DEVICE_REMOVED if a new driver is installed while your application is running, or if you are running on a 'GPU is in the dock' style laptop and the laptop is undocked. You can test this case by opening the Developer Command Prompt for Visual Studio as an administrator, and typing dxcap -forcetdr which will immediately cause all currently running Direct3D apps to get a DXGI_ERROR_DEVICE_REMOVED event.

Smart-pointer

We make use of the Microsoft::WRL::ComPtr smart-pointer for managing the lifetime of the Direct3D 12 COM objects, which is why we make use of .Get() in the code above. See ComPtr and Microsoft Docs for more information and usage.

Error handling

Many Direct3D functions return an HRESULT which is the standard for COM APIs. For robustness and easier debugging, it is important that you always check the result of every function that return an HRESULT. If you really can safely assume there is no error condition for a particular function, the function itself will return void instead of HRESULT.

The Win32 game template makes use of the helper function ThrowIfFailed in the DX C++ namespace declared in pch.h. This is the same helper that is used by the Windows Store and Windows phone VS templates. This helper throws a C++ exception if the standard FAILED macro returns true for a given HRESULT. This is used for fail fast error handling.

DX::ThrowIfFailed(device->CreateCommittedResource(
    &heapProperties,
    D3D12_HEAP_FLAG_NONE,
    &depthStencilDesc,
    D3D12_RESOURCE_STATE_DEPTH_WRITE,
    &depthOptimizedClearValue,
    IID_PPV_ARGS(m_depthStencil.ReleaseAndGetAddressOf())
    ));

Do not use hr == S_OK to check for success. Use SUCCEEDED(hr) instead.

The DR VS template variants include the enhanced version of ThrowIfFailed.

Click here for Xbox development note

Note that due to the use of the 'monolithic' DirectX 12.X Runtime, you will need to use IID_GRAPHICS_PPV_ARGS instead of IID_PPV_ARGS for Xbox One XDK / Microsoft GDKX development. See DirectXHelpers.

Gamma

The DeviceResources implementation supports using DXGI_FORMAT_*_SRGB formats for the backbuffer using the method compatible with modern swap effects. See The Care and Feeding of Modern Swap Chains for more details.

Fullscreen

The Win32 desktop and UWP templates implement immersive fullscreen. You can toggle this using the traditional hotkey Alt+Enter. If you want to default to full-screen at startup, see the TODO comments in Main.cpp.

Message 'pump'

For the Win32 desktop versions of the template, the Main.cpp source file contains the WndProc and the basic loop:

MSG msg = {};
while (WM_QUIT != msg.message)
{
    if (PeekMessage(&msg, nullptr, 0, 0, PM_REMOVE))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    else
    {
        g_game->Tick();
    }
}

This ensures that all pending Win32 messages are consumed before updating/rendering the next frame. This is critical for maintaining responsiveness.

For UWP, the equivalent thing is done inside the ViewProvider Run method.

Next lesson: Adding the DirectX Tool Kit

Further reading

Direct3D Win32 Game Visual Studio template
Direct3D Game Visual Studio templates (Redux)
Anatomy of Direct3D 12 Create Device
Manifest Madness
64-bit programming for Game Developers