/// <summary>
/// Updates resources associated with a holographic camera's swap chain.
/// The app does not access the swap chain directly, but it does create
/// resource views for the back buffer.
/// </summary>
public void CreateResourcesForBackBuffer(
DeviceResources deviceResources,
HolographicCameraRenderingParameters cameraParameters
)
{
var device = deviceResources.D3DDevice;
// Get the WinRT object representing the holographic camera's back buffer.
var surface = cameraParameters.Direct3D11BackBuffer;
// Get a DXGI interface for the holographic camera's back buffer.
// Holographic cameras do not provide the DXGI swap chain, which is owned
// by the system. The Direct3D back buffer resource is provided using WinRT
// interop APIs.
var surfaceDxgiInterfaceAccess = surface as InteropStatics.IDirect3DDxgiInterfaceAccess;
var pResource = surfaceDxgiInterfaceAccess.GetInterface(InteropStatics.Id3D11Resource);
var resource = CppObject.FromPointer <Resource>(pResource);
Marshal.Release(pResource);
// Get a Direct3D interface for the holographic camera's back buffer.
var cameraBackBuffer = resource.QueryInterface <Texture2D>();
// Determine if the back buffer has changed. If so, ensure that the render target view
// is for the current back buffer.
if ((null == _d3DBackBuffer) || (_d3DBackBuffer.NativePointer != cameraBackBuffer.NativePointer))
{
// This can change every frame as the system moves to the next buffer in the
// swap chain. This mode of operation will occur when certain rendering modes
// are activated.
_d3DBackBuffer = cameraBackBuffer;
// Create a render target view of the back buffer.
// Creating this resource is inexpensive, and is better than keeping track of
// the back buffers in order to pre-allocate render target views for each one.
_d3DRenderTargetView = this.ToDispose(new RenderTargetView(device, BackBufferTexture2D));
// Get the DXGI format for the back buffer.
// This information can be accessed by the app using CameraResources::GetBackBufferDXGIFormat().
var backBufferDesc = BackBufferTexture2D.Description;
_dxgiFormat = backBufferDesc.Format;
// Check for render target size changes.
var currentSize = _holographicCamera.RenderTargetSize;
if (_d3DRenderTargetSize != currentSize)
{
// Set render target size.
_d3DRenderTargetSize = HolographicCamera.RenderTargetSize;
// A new depth stencil view is also needed.
this.RemoveAndDispose(ref _d3DDepthStencilView);
}
}
// Refresh depth stencil resources, if needed.
if (null == DepthStencilView)
{
// Create a depth stencil view for use with 3D rendering if needed.
var depthStencilDesc = new Texture2DDescription {
Format = SharpDX.DXGI.Format.D16_UNorm,
Width = (int)RenderTargetSize.Width,
Height = (int)RenderTargetSize.Height,
ArraySize = IsRenderingStereoscopic ? 2 : 1, // Create two textures when rendering in stereo.
MipLevels = 1, // Use a single mipmap level.
BindFlags = BindFlags.DepthStencil,
SampleDescription = new SharpDX.DXGI.SampleDescription(1, 0)
};
using (var depthStencil = new Texture2D(device, depthStencilDesc)) {
var depthStencilViewDesc = new DepthStencilViewDescription {
Dimension = IsRenderingStereoscopic ? DepthStencilViewDimension.Texture2DArray : DepthStencilViewDimension.Texture2D,
Texture2DArray =
{
ArraySize = IsRenderingStereoscopic ? 2 : 0
}
};
_d3DDepthStencilView = this.ToDispose(new DepthStencilView(device, depthStencil, depthStencilViewDesc));
}
}
// Create the constant buffer, if needed.
if (null == _viewProjectionConstantBuffer)
{
// Create a constant buffer to store view and projection matrices for the camera.
var viewProjectionConstantBufferData = new ViewProjectionConstantBuffer();
_viewProjectionConstantBuffer = this.ToDispose(Buffer.Create(
device,
BindFlags.ConstantBuffer,
ref viewProjectionConstantBufferData));
}
}
/// <summary>
/// Updates the constant buffer for the display with view and projection
/// matrices for the current frame.
/// </summary>
public void UpdateViewProjectionBuffer(
DeviceResources deviceResources,
HolographicCameraPose cameraPose,
SpatialCoordinateSystem coordinateSystem
)
{
// The system changes the viewport on a per-frame basis for system optimizations.
_d3DViewport.X = (float)cameraPose.Viewport.Left;
_d3DViewport.Y = (float)cameraPose.Viewport.Top;
_d3DViewport.Width = (float)cameraPose.Viewport.Width;
_d3DViewport.Height = (float)cameraPose.Viewport.Height;
_d3DViewport.MinDepth = 0;
_d3DViewport.MaxDepth = 1;
// The projection transform for each frame is provided by the HolographicCameraPose.
var cameraProjectionTransform = cameraPose.ProjectionTransform;
// Get a container object with the view and projection matrices for the given
// pose in the given coordinate system.
var viewTransformContainer = cameraPose.TryGetViewTransform(coordinateSystem);
// If TryGetViewTransform returns null, 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.
var viewProjectionConstantBufferData = new ViewProjectionConstantBuffer();
var viewTransformAcquired = viewTransformContainer.HasValue;
if (viewTransformAcquired)
{
// Otherwise, the set of view transforms can be retrieved.
var 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.
viewProjectionConstantBufferData.ViewProjectionLeft = Matrix4x4.Transpose(
viewCoordinateSystemTransform.Left * cameraProjectionTransform.Left
);
viewProjectionConstantBufferData.ViewProjectionRight = Matrix4x4.Transpose(
viewCoordinateSystemTransform.Right * cameraProjectionTransform.Right
);
}
// Use the D3D device context to update Direct3D device-based resources.
var context = deviceResources.D3DDeviceContext;
// Loading is asynchronous. Resources must be created before they can be updated.
if (context == null || _viewProjectionConstantBuffer == null || !viewTransformAcquired)
{
_framePending = false;
}
else
{
// Update the view and projection matrices.
context.UpdateSubresource(ref viewProjectionConstantBufferData, _viewProjectionConstantBuffer);
_framePending = true;
}
}
