Rendering in DirectX
Note
This article relates to the legacy WinRT native APIs. For new native app projects, we recommend using the OpenXR API.
Windows Mixed Reality is built on DirectX to produce rich, 3D graphical experiences for users. The rendering abstraction sits just above DirectX, which lets apps reason about the position and orientation of holographic scene observers predicted by the system. The developer can then locate their holograms based on each camera, letting the app render these holograms in various spatial coordinate systems as the user moves around.
Note: This walkthrough describes holographic rendering in Direct3D 11. A Direct3D 12 Windows Mixed Reality app template is also supplied with the Mixed Reality app templates extension.
Update for the current frame
To update the application state for holograms, once per frame the app will:
- Get a HolographicFrame from the display management system.
- Update the scene with the current prediction of where the camera view will be when render is completed. Note, there can be more than one camera for the holographic scene.
To render to holographic camera views, once per frame the app will:
- For each camera, render the scene for the current frame, using the camera view and projection matrices from the system.
Create a new holographic frame and get its prediction
The HolographicFrame has information that the app needs to update and render the current frame. The app begins each new frame by calling the CreateNextFrame method. When this method is called, predictions are made using the latest sensor data available, and encapsulated in CurrentPrediction object.
A new frame object must be used for each rendered frame as it is only valid for an instant in time. The CurrentPrediction property contains information such as the camera position. The information is extrapolated to the exact moment in time when the frame is expected to be visible to the user.
The following code is excerpted from AppMain::Update:
// The HolographicFrame has information that the app needs in order
// to update and render the current frame. The app begins each new
// frame by calling CreateNextFrame.
HolographicFrame holographicFrame = m_holographicSpace.CreateNextFrame();
// Get a prediction of where holographic cameras will be when this frame
// is presented.
HolographicFramePrediction prediction = holographicFrame.CurrentPrediction();
Process camera updates
Back buffers can change from frame to frame. Your app needs to validate the back buffer for each camera, and release and recreate resource views and depth buffers as needed. Notice that the set of poses in the prediction is the authoritative list of cameras being used in the current frame. Usually, you use this list to iterate on the set of cameras.
From AppMain::Update:
m_deviceResources->EnsureCameraResources(holographicFrame, prediction);
From DeviceResources::EnsureCameraResources:
for (HolographicCameraPose const& cameraPose : prediction.CameraPoses())
{
HolographicCameraRenderingParameters renderingParameters = frame.GetRenderingParameters(cameraPose);
CameraResources* pCameraResources = cameraResourceMap[cameraPose.HolographicCamera().Id()].get();
pCameraResources->CreateResourcesForBackBuffer(this, renderingParameters);
}
Get the coordinate system to use as a basis for rendering
Windows Mixed Reality lets your app create various coordinate systems, like attached and stationary reference frames for tracking locations in the physical world. Your app can then use these coordinate systems to reason about where to render holograms each frame. When requesting coordinates from an API, you'll always pass in the SpatialCoordinateSystem within which you want those coordinates to be expressed.
From AppMain::Update:
pose = SpatialPointerPose::TryGetAtTimestamp(
m_stationaryReferenceFrame.CoordinateSystem(), prediction.Timestamp());
These coordinate systems can then be used to generate stereo view matrices when rendering the content in your scene.
From CameraResources::UpdateViewProjectionBuffer:
// Get a container object with the view and projection matrices for the given
// pose in the given coordinate system.
auto viewTransformContainer = cameraPose.TryGetViewTransform(coordinateSystem);
Process gaze and gesture input
Gaze and hand input aren't time-based and don't have to update in the StepTimer function. However this input is something that the app needs to look at each frame.
Process time-based updates
Any real-time rendering app will need some way to process time-based updates - the Windows Holographic app template uses a StepTimer implementation, similar to the StepTimer provided in the DirectX 11 UWP app template. This StepTimer sample helper class can provide fixed time-step updates, variable time-step updates, and the default mode is variable time steps.
For holographic rendering, we've chosen not to put too much into the timer function because you can configure it to be a fixed time step. It might get called more than once per frame – or not at all, for some frames – and our holographic data updates should happen once per frame.
From AppMain::Update:
m_timer.Tick([this]()
{
m_spinningCubeRenderer->Update(m_timer);
});
Position and rotate holograms in your coordinate system
If you're operating in a single coordinate system, as the template does with the SpatialStationaryReferenceFrame, this process isn't different from what you're otherwise used to in 3D graphics. Here, we rotate the cube and set the model matrix based on the position in the stationary coordinate system.
From SpinningCubeRenderer::Update:
// Rotate the cube.
// Convert degrees to radians, then convert seconds to rotation angle.
const float radiansPerSecond = XMConvertToRadians(m_degreesPerSecond);
const double totalRotation = timer.GetTotalSeconds() * radiansPerSecond;
const float radians = static_cast<float>(fmod(totalRotation, XM_2PI));
const XMMATRIX modelRotation = XMMatrixRotationY(-radians);
// Position the cube.
const XMMATRIX modelTranslation = XMMatrixTranslationFromVector(XMLoadFloat3(&m_position));
// Multiply to get the transform matrix.
// Note that this transform does not enforce a particular coordinate system. The calling
// class is responsible for rendering this content in a consistent manner.
const XMMATRIX modelTransform = XMMatrixMultiply(modelRotation, modelTranslation);
// The view and projection matrices are provided by the system; they are associated
// with holographic cameras, and updated on a per-camera basis.
// Here, we provide the model transform for the sample hologram. The model transform
// matrix is transposed to prepare it for the shader.
XMStoreFloat4x4(&m_modelConstantBufferData.model, XMMatrixTranspose(modelTransform));
Note about advanced scenarios: The spinning cube is a simple example of how to position a hologram within a single reference frame. It's also possible to use multiple SpatialCoordinateSystems in the same rendered frame, at the same time.
Update constant buffer data
Model transforms for content are updated as usual. By now, you'll have computed valid transforms for the coordinate system you'll be rendering in.
From SpinningCubeRenderer::Update:
// Update the model transform buffer for the hologram.
context->UpdateSubresource(
m_modelConstantBuffer.Get(),
0,
nullptr,
&m_modelConstantBufferData,
0,
0
);
What about view and projection transforms? For best results, we want to wait until we're almost ready for our draw calls before we get these.
Render the current frame
Rendering on Windows Mixed Reality isn't much different from rendering on a 2D mono display, but there are a few differences:
- Holographic frame predictions are important. The closer the prediction is to when your frame is presented, the better your holograms will look.
- Windows Mixed Reality controls the camera views. Render to each one because the holographic frame will be presenting them for you later.
- We recommend doing stereo rendering using instanced drawing to a render target array. The holographic app template uses the recommended approach of instanced drawing to a render target array, which uses a render target view onto a Texture2DArray.
- If you want to render without using stereo instancing, you'll need to create two non-array RenderTargetViews, one for each eye. Each RenderTargetViews references one of the two slices in the Texture2DArray provided to the app from the system. This isn't recommended, as it's typically slower than using instancing.
Get an updated HolographicFrame prediction
Updating the frame prediction enhances the effectiveness of image stabilization. You get more accurate positioning of holograms because of the shorter time between the prediction and when the frame is visible to the user. Ideally update your frame prediction just before rendering.
holographicFrame.UpdateCurrentPrediction();
HolographicFramePrediction prediction = holographicFrame.CurrentPrediction();
Render to each camera
Loop on the set of camera poses in the prediction, and render to each camera in this set.
Set up your rendering pass
Windows Mixed Reality uses stereoscopic rendering to enhance the illusion of depth and to render stereoscopically, so both the left and the right display are active. With stereoscopic rendering, there's an offset between the two displays, which the brain can reconcile as actual depth. This section covers stereoscopic rendering using instancing, using code from the Windows Holographic app template.
Each camera has its own render target (back buffer), and view and projection matrices, into the holographic space. Your app will need to create any other camera-based resources - such as the depth buffer - on a per-camera basis. In the Windows Holographic app template, we provide a helper class to bundle these resources together in DX::CameraResources. Start by setting up the render target views:
From AppMain::Render:
// This represents the device-based resources for a HolographicCamera.
DX::CameraResources* pCameraResources = cameraResourceMap[cameraPose.HolographicCamera().Id()].get();
// Get the device context.
const auto context = m_deviceResources->GetD3DDeviceContext();
const auto depthStencilView = pCameraResources->GetDepthStencilView();
// Set render targets to the current holographic camera.
ID3D11RenderTargetView *const targets[1] =
{ pCameraResources->GetBackBufferRenderTargetView() };
context->OMSetRenderTargets(1, targets, depthStencilView);
// Clear the back buffer and depth stencil view.
if (m_canGetHolographicDisplayForCamera &&
cameraPose.HolographicCamera().Display().IsOpaque())
{
context->ClearRenderTargetView(targets[0], DirectX::Colors::CornflowerBlue);
}
else
{
context->ClearRenderTargetView(targets[0], DirectX::Colors::Transparent);
}
context->ClearDepthStencilView(
depthStencilView, D3D11_CLEAR_DEPTH | D3D11_CLEAR_STENCIL, 1.0f, 0);
Use the prediction to get the view and projection matrices for the camera
The view and projection matrices for each holographic camera will change with every frame. Refresh the data in the constant buffer for each holographic camera. Do this after you updated the prediction, and before you make any draw calls for that camera.
From AppMain::Render:
// The view and projection matrices for each holographic camera will change
// every frame. This function refreshes the data in the constant buffer for
// the holographic camera indicated by cameraPose.
if (m_stationaryReferenceFrame)
{
pCameraResources->UpdateViewProjectionBuffer(
m_deviceResources, cameraPose, m_stationaryReferenceFrame.CoordinateSystem());
}
// Attach the view/projection constant buffer for this camera to the graphics pipeline.
bool cameraActive = pCameraResources->AttachViewProjectionBuffer(m_deviceResources);
Here, we show how the matrices are acquired from the camera pose. During this process, we also obtain the current viewport for the camera. Note how we provide a coordinate system: this is the same coordinate system we used to understand gaze, and it's the same one we used to position the spinning cube.
From CameraResources::UpdateViewProjectionBuffer:
// The system changes the viewport on a per-frame basis for system optimizations.
auto viewport = cameraPose.Viewport();
m_d3dViewport = CD3D11_VIEWPORT(
viewport.X,
viewport.Y,
viewport.Width,
viewport.Height
);
// The projection transform for each frame is provided by the HolographicCameraPose.
HolographicStereoTransform cameraProjectionTransform = cameraPose.ProjectionTransform();
// Get a container object with the view and projection matrices for the given
// pose in the given coordinate system.
auto viewTransformContainer = cameraPose.TryGetViewTransform(coordinateSystem);
// If TryGetViewTransform returns a null pointer, that means the pose and coordinate
// system cannot be understood relative to one another; content cannot be rendered
// in this coordinate system for the duration of the current frame.
// This usually means that positional tracking is not active for the current frame, in
// which case it is possible to use a SpatialLocatorAttachedFrameOfReference to render
// content that is not world-locked instead.
DX::ViewProjectionConstantBuffer viewProjectionConstantBufferData;
bool viewTransformAcquired = viewTransformContainer != nullptr;
if (viewTransformAcquired)
{
// Otherwise, the set of view transforms can be retrieved.
HolographicStereoTransform viewCoordinateSystemTransform = viewTransformContainer.Value();
// Update the view matrices. Holographic cameras (such as Microsoft HoloLens) are
// constantly moving relative to the world. The view matrices need to be updated
// every frame.
XMStoreFloat4x4(
&viewProjectionConstantBufferData.viewProjection[0],
XMMatrixTranspose(XMLoadFloat4x4(&viewCoordinateSystemTransform.Left) *
XMLoadFloat4x4(&cameraProjectionTransform.Left))
);
XMStoreFloat4x4(
&viewProjectionConstantBufferData.viewProjection[1],
XMMatrixTranspose(XMLoadFloat4x4(&viewCoordinateSystemTransform.Right) *
XMLoadFloat4x4(&cameraProjectionTransform.Right))
);
}
The viewport should be set each frame. Your vertex shader (at least) will generally need access to the view/projection data.
From CameraResources::AttachViewProjectionBuffer:
// Set the viewport for this camera.
context->RSSetViewports(1, &m_d3dViewport);
// Send the constant buffer to the vertex shader.
context->VSSetConstantBuffers(
1,
1,
m_viewProjectionConstantBuffer.GetAddressOf()
);
Render to the camera back buffer and commit the depth buffer:
It's a good idea to check that TryGetViewTransform succeeded before trying to use the view/projection data, because if the coordinate system isn't locatable (for example, tracking was interrupted) your app can't render with it for that frame. The template only calls Render on the spinning cube if the CameraResources class indicates a successful update.
Windows Mixed Reality includes features for image stabilization to keep holograms positioned where a developer or user puts them in the world. Image stabilization helps hide the latency inherent in a rendering pipeline to ensure the best holographic experiences for users. A focus point may be specified to enhance image stabilization even further, or a depth buffer may be provided to compute optimized image stabilization in real time.
For best results, your app should provide a depth buffer using the CommitDirect3D11DepthBuffer API. Windows Mixed Reality can then use geometry information from the depth buffer to optimize image stabilization in real time. The Windows Holographic app template commits the app's depth buffer by default, helping optimize hologram stability.
From AppMain::Render:
// Only render world-locked content when positional tracking is active.
if (cameraActive)
{
// Draw the sample hologram.
m_spinningCubeRenderer->Render();
if (m_canCommitDirect3D11DepthBuffer)
{
// On versions of the platform that support the CommitDirect3D11DepthBuffer API, we can
// provide the depth buffer to the system, and it will use depth information to stabilize
// the image at a per-pixel level.
HolographicCameraRenderingParameters renderingParameters =
holographicFrame.GetRenderingParameters(cameraPose);
IDirect3DSurface interopSurface =
DX::CreateDepthTextureInteropObject(pCameraResources->GetDepthStencilTexture2D());
// Calling CommitDirect3D11DepthBuffer causes the system to queue Direct3D commands to
// read the depth buffer. It will then use that information to stabilize the image as
// the HolographicFrame is presented.
renderingParameters.CommitDirect3D11DepthBuffer(interopSurface);
}
}
Note
Windows will process your depth texture on the GPU, so it must be possible to use your depth buffer as a shader resource. The ID3D11Texture2D that you create should be in a typeless format and it should be bound as a shader resource view. Here is an example of how to create a depth texture that can be committed for image stabilization.
Code for Depth buffer resource creation for CommitDirect3D11DepthBuffer:
// Create a depth stencil view for use with 3D rendering if needed.
CD3D11_TEXTURE2D_DESC depthStencilDesc(
DXGI_FORMAT_R16_TYPELESS,
static_cast<UINT>(m_d3dRenderTargetSize.Width),
static_cast<UINT>(m_d3dRenderTargetSize.Height),
m_isStereo ? 2 : 1, // Create two textures when rendering in stereo.
1, // Use a single mipmap level.
D3D11_BIND_DEPTH_STENCIL | D3D11_BIND_SHADER_RESOURCE
);
winrt::check_hresult(
device->CreateTexture2D(
&depthStencilDesc,
nullptr,
&m_d3dDepthStencil
));
CD3D11_DEPTH_STENCIL_VIEW_DESC depthStencilViewDesc(
m_isStereo ? D3D11_DSV_DIMENSION_TEXTURE2DARRAY : D3D11_DSV_DIMENSION_TEXTURE2D,
DXGI_FORMAT_D16_UNORM
);
winrt::check_hresult(
device->CreateDepthStencilView(
m_d3dDepthStencil.Get(),
&depthStencilViewDesc,
&m_d3dDepthStencilView
));
Draw holographic content
The Windows Holographic app template renders content in stereo by using the recommended technique of drawing instanced geometry to a Texture2DArray of size 2. Let's look at the instancing part of this, and how it works on Windows Mixed Reality.
From SpinningCubeRenderer::Render:
// Draw the objects.
context->DrawIndexedInstanced(
m_indexCount, // Index count per instance.
2, // Instance count.
0, // Start index location.
0, // Base vertex location.
0 // Start instance location.
);
Each instance accesses a different view/projection matrix from the constant buffer. Here's the constant buffer structure, which is just an array of two matrices.
From VertexShaderShared.hlsl, included by VPRTVertexShader.hlsl:
// A constant buffer that stores each set of view and projection matrices in column-major format.
cbuffer ViewProjectionConstantBuffer : register(b1)
{
float4x4 viewProjection[2];
};
The render target array index must be set for each pixel. In the following snippet, output.viewId is mapped to the SV_RenderTargetArrayIndex semantic. This requires support for an optional Direct3D 11.3 feature, which allows the render target array index semantic to be set from any shader stage.
From VPRTVertexShader.hlsl:
// Per-vertex data passed to the geometry shader.
struct VertexShaderOutput
{
min16float4 pos : SV_POSITION;
min16float3 color : COLOR0;
// The render target array index is set here in the vertex shader.
uint viewId : SV_RenderTargetArrayIndex;
};
From VertexShaderShared.hlsl, included by VPRTVertexShader.hlsl:
// Per-vertex data used as input to the vertex shader.
struct VertexShaderInput
{
min16float3 pos : POSITION;
min16float3 color : COLOR0;
uint instId : SV_InstanceID;
};
// Simple shader to do vertex processing on the GPU.
VertexShaderOutput main(VertexShaderInput input)
{
VertexShaderOutput output;
float4 pos = float4(input.pos, 1.0f);
// Note which view this vertex has been sent to. Used for matrix lookup.
// Taking the modulo of the instance ID allows geometry instancing to be used
// along with stereo instanced drawing; in that case, two copies of each
// instance would be drawn, one for left and one for right.
int idx = input.instId % 2;
// Transform the vertex position into world space.
pos = mul(pos, model);
// Correct for perspective and project the vertex position onto the screen.
pos = mul(pos, viewProjection[idx]);
output.pos = (min16float4)pos;
// Pass the color through without modification.
output.color = input.color;
// Set the render target array index.
output.viewId = idx;
return output;
}
If you want to use your existing instanced drawing techniques with this method of drawing to a stereo render target array, draw twice the number of instances you normally have. In the shader, divide input.instId by 2 to get the original instance ID, which can be indexed into (for example) a buffer of per-object data: int actualIdx = input.instId / 2;
Important note about rendering stereo content on HoloLens
Windows Mixed Reality supports the ability to set the render target array index from any shader stage. Normally, this is a task that could only be done in the geometry shader stage because of the way the semantic is defined for Direct3D 11. Here, we show a complete example of how to set up a rendering pipeline with just the vertex and pixel shader stages set. The shader code is as described above.
From SpinningCubeRenderer::Render:
const auto context = m_deviceResources->GetD3DDeviceContext();
// Each vertex is one instance of the VertexPositionColor struct.
const UINT stride = sizeof(VertexPositionColor);
const UINT offset = 0;
context->IASetVertexBuffers(
0,
1,
m_vertexBuffer.GetAddressOf(),
&stride,
&offset
);
context->IASetIndexBuffer(
m_indexBuffer.Get(),
DXGI_FORMAT_R16_UINT, // Each index is one 16-bit unsigned integer (short).
0
);
context->IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_TRIANGLELIST);
context->IASetInputLayout(m_inputLayout.Get());
// Attach the vertex shader.
context->VSSetShader(
m_vertexShader.Get(),
nullptr,
0
);
// Apply the model constant buffer to the vertex shader.
context->VSSetConstantBuffers(
0,
1,
m_modelConstantBuffer.GetAddressOf()
);
// Attach the pixel shader.
context->PSSetShader(
m_pixelShader.Get(),
nullptr,
0
);
// Draw the objects.
context->DrawIndexedInstanced(
m_indexCount, // Index count per instance.
2, // Instance count.
0, // Start index location.
0, // Base vertex location.
0 // Start instance location.
);
Important note about rendering on non-HoloLens devices
Setting the render target array index in the vertex shader requires that the graphics driver supports an optional Direct3D 11.3 feature, which HoloLens does support. Your app may can safely implement just that technique for rendering, and all requirements will be met for running on the Microsoft HoloLens.
It may be the case that you want to use the HoloLens emulator as well, which can be a powerful development tool for your holographic app - and support Windows Mixed Reality immersive headset devices that are attached to Windows 10 PCs. Support for the non-HoloLens rendering path - for all of Windows Mixed Reality - is also built into the Windows Holographic app template. In the template code, you'll find code to enable your holographic app to run on the GPU in your development PC. Here's how the DeviceResources class checks for this optional feature support.
From DeviceResources::CreateDeviceResources:
// Check for device support for the optional feature that allows setting the render target array index from the vertex shader stage.
D3D11_FEATURE_DATA_D3D11_OPTIONS3 options;
m_d3dDevice->CheckFeatureSupport(D3D11_FEATURE_D3D11_OPTIONS3, &options, sizeof(options));
if (options.VPAndRTArrayIndexFromAnyShaderFeedingRasterizer)
{
m_supportsVprt = true;
}
To support rendering without this optional feature, your app must use a geometry shader to set the render target array index. This snippet would be added after VSSetConstantBuffers, and before PSSetShader in the code example shown in the previous section that explains how to render stereo on HoloLens.
From SpinningCubeRenderer::Render:
if (!m_usingVprtShaders)
{
// On devices that do not support the D3D11_FEATURE_D3D11_OPTIONS3::
// VPAndRTArrayIndexFromAnyShaderFeedingRasterizer optional feature,
// a pass-through geometry shader is used to set the render target
// array index.
context->GSSetShader(
m_geometryShader.Get(),
nullptr,
0
);
}
HLSL NOTE: In this case, you must also load a slightly modified vertex shader that passes the render target array index to the geometry shader using an always-allowed shader semantic, such as TEXCOORD0. The geometry shader doesn't have to do any work; the template geometry shader passes through all data, with the exception of the render target array index, which is used to set the SV_RenderTargetArrayIndex semantic.
App template code for GeometryShader.hlsl:
// Per-vertex data from the vertex shader.
struct GeometryShaderInput
{
min16float4 pos : SV_POSITION;
min16float3 color : COLOR0;
uint instId : TEXCOORD0;
};
// Per-vertex data passed to the rasterizer.
struct GeometryShaderOutput
{
min16float4 pos : SV_POSITION;
min16float3 color : COLOR0;
uint rtvId : SV_RenderTargetArrayIndex;
};
// This geometry shader is a pass-through that leaves the geometry unmodified
// and sets the render target array index.
[maxvertexcount(3)]
void main(triangle GeometryShaderInput input[3], inout TriangleStream<GeometryShaderOutput> outStream)
{
GeometryShaderOutput output;
[unroll(3)]
for (int i = 0; i < 3; ++i)
{
output.pos = input[i].pos;
output.color = input[i].color;
output.rtvId = input[i].instId;
outStream.Append(output);
}
}
Present
Enable the holographic frame to present the swap chain
With Windows Mixed Reality, the system controls the swap chain. The system then manages presenting frames to each holographic camera to ensure a high-quality user experience. It also provides a viewport update each frame, for each camera, to optimize aspects of the system such as image stabilization or Mixed Reality Capture. So, a holographic app using DirectX doesn't call Present on a DXGI swap chain. Instead, you use the HolographicFrame class to present all swapchains for a frame once you're done drawing it.
From DeviceResources::Present:
HolographicFramePresentResult presentResult = frame.PresentUsingCurrentPrediction();
By default, this API waits for the frame to finish before it returns. Holographic apps should wait for the previous frame to finish before starting work on a new frame, because this reduces latency and allows for better results from holographic frame predictions. This isn't a hard rule, and if you have frames that take longer than one screen refresh to render you can disable this wait by passing the HolographicFramePresentWaitBehavior parameter to PresentUsingCurrentPrediction. In this case, you would likely use an asynchronous rendering thread to maintain a continuous load on the GPU. The refresh rate of the HoloLens device is 60 hz, where one frame has a duration of approximately 16 ms. Immersive headset devices can range from 60 hz to 90 hz; when refreshing the display at 90 hz, each frame will have a duration of approximately 11 ms.
Handle DeviceLost scenarios in cooperation with the HolographicFrame
DirectX 11 apps would typically want to check the HRESULT returned by the DXGI swap chain's Present function to find out if there was a DeviceLost error. The HolographicFrame class handles this for you. Inspect the returned HolographicFramePresentResult to find out if you need to release and recreate the Direct3D device and device-based resources.
// The PresentUsingCurrentPrediction API will detect when the graphics device
// changes or becomes invalid. When this happens, it is considered a Direct3D
// device lost scenario.
if (presentResult == HolographicFramePresentResult::DeviceRemoved)
{
// The Direct3D device, context, and resources should be recreated.
HandleDeviceLost();
}
If the Direct3D device was lost, and you did recreate it, you have to tell the HolographicSpace to start using the new device. The swap chain will be recreated for this device.
From DeviceResources::InitializeUsingHolographicSpace:
m_holographicSpace.SetDirect3D11Device(m_d3dInteropDevice);
Once your frame is presented, you can return back to the main program loop and allow it to continue to the next frame.
Hybrid graphics PCs and mixed reality applications
Windows 10 Creators Update PCs may be configured with both discrete and integrated GPUs. With these types of computers, Windows will choose the adapter the headset is connected to. Applications must ensure the DirectX device it creates uses the same adapter.
Most general Direct3D sample code demonstrates creating a DirectX device using the default hardware adapter, which on a hybrid system may not be the same as the one used for the headset.
To work around any issues, use the HolographicAdapterID from either HolographicSpace.PrimaryAdapterId() or HolographicDisplay.AdapterId(). This adapterId can then be used to select the right DXGIAdapter using IDXGIFactory4.EnumAdapterByLuid.
From DeviceResources::InitializeUsingHolographicSpace:
// The holographic space might need to determine which adapter supports
// holograms, in which case it will specify a non-zero PrimaryAdapterId.
LUID id =
{
m_holographicSpace.PrimaryAdapterId().LowPart,
m_holographicSpace.PrimaryAdapterId().HighPart
};
// When a primary adapter ID is given to the app, the app should find
// the corresponding DXGI adapter and use it to create Direct3D devices
// and device contexts. Otherwise, there is no restriction on the DXGI
// adapter the app can use.
if ((id.HighPart != 0) || (id.LowPart != 0))
{
UINT createFlags = 0;
// Create the DXGI factory.
ComPtr<IDXGIFactory1> dxgiFactory;
winrt::check_hresult(
CreateDXGIFactory2(
createFlags,
IID_PPV_ARGS(&dxgiFactory)
));
ComPtr<IDXGIFactory4> dxgiFactory4;
winrt::check_hresult(dxgiFactory.As(&dxgiFactory4));
// Retrieve the adapter specified by the holographic space.
winrt::check_hresult(
dxgiFactory4->EnumAdapterByLuid(
id,
IID_PPV_ARGS(&m_dxgiAdapter)
));
}
else
{
m_dxgiAdapter.Reset();
}
Code to update DeviceResources::CreateDeviceResources to use IDXGIAdapter
// Create the Direct3D 11 API device object and a corresponding context.
ComPtr<ID3D11Device> device;
ComPtr<ID3D11DeviceContext> context;
const D3D_DRIVER_TYPE driverType = m_dxgiAdapter == nullptr ? D3D_DRIVER_TYPE_HARDWARE : D3D_DRIVER_TYPE_UNKNOWN;
const HRESULT hr = D3D11CreateDevice(
m_dxgiAdapter.Get(), // Either nullptr, or the primary adapter determined by Windows Holographic.
driverType, // Create a device using the hardware graphics driver.
0, // Should be 0 unless the driver is D3D_DRIVER_TYPE_SOFTWARE.
creationFlags, // Set debug and Direct2D compatibility flags.
featureLevels, // List of feature levels this app can support.
ARRAYSIZE(featureLevels), // Size of the list above.
D3D11_SDK_VERSION, // Always set this to D3D11_SDK_VERSION for Windows Runtime apps.
&device, // Returns the Direct3D device created.
&m_d3dFeatureLevel, // Returns feature level of device created.
&context // Returns the device immediate context.
);
Hybrid graphics and Media Foundation
Using Media Foundation on hybrid systems may cause issues where video won't render or video texture are corrupt because Media Foundation is defaulting to a system behavior. In some scenarios, creating a separate ID3D11Device is required to support multi-threading and the correct creation flags are set.
When initializing the ID3D11Device, D3D11_CREATE_DEVICE_VIDEO_SUPPORT flag must be defined as part of the D3D11_CREATE_DEVICE_FLAG. Once the device and context is created, call SetMultithreadProtected to enable multithreading. To associate the device with the IMFDXGIDeviceManager, use the IMFDXGIDeviceManager::ResetDevice function.
Code to associate a ID3D11Device with IMFDXGIDeviceManager:
// create dx device for media pipeline
winrt::com_ptr<ID3D11Device> spMediaDevice;
// See above. Also make sure to enable the following flags on the D3D11 device:
// * D3D11_CREATE_DEVICE_VIDEO_SUPPORT
// * D3D11_CREATE_DEVICE_BGRA_SUPPORT
if (FAILED(CreateMediaDevice(spAdapter.get(), &spMediaDevice)))
return;
// Turn multithreading on
winrt::com_ptr<ID3D10Multithread> spMultithread;
if (spContext.try_as(spMultithread))
{
spMultithread->SetMultithreadProtected(TRUE);
}
// lock the shared dxgi device manager
// call MFUnlockDXGIDeviceManager when no longer needed
UINT uiResetToken;
winrt::com_ptr<IMFDXGIDeviceManager> spDeviceManager;
hr = MFLockDXGIDeviceManager(&uiResetToken, spDeviceManager.put());
if (FAILED(hr))
return hr;
// associate the device with the manager
hr = spDeviceManager->ResetDevice(spMediaDevice.get(), uiResetToken);
if (FAILED(hr))
return hr;