/// <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,
            ref HolographicCameraRenderingParameters cameraParameters
            )
        {
            var device = deviceResources.D3DDevice;

            // Get the WinRT object representing the holographic camera's back buffer.
            IDirect3DSurface 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.
            InteropStatics.IDirect3DDxgiInterfaceAccess surfaceDxgiInterfaceAccess = surface as InteropStatics.IDirect3DDxgiInterfaceAccess;
            IntPtr pResource = surfaceDxgiInterfaceAccess.GetInterface(InteropStatics.ID3D11Resource);

            // 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 != pResource))
            {
                // Clean up references to previous resources.
                this.RemoveAndDispose(ref d3dBackBuffer);
                this.RemoveAndDispose(ref d3dRenderTargetView);

                // 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 = this.ToDispose(new SharpDX.Direct3D11.Texture2D(pResource));

                // 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, d3dBackBuffer));

                // Get the DXGI format for the back buffer.
                // This information can be accessed by the app using CameraResources::GetBackBufferDXGIFormat().
                Texture2DDescription backBufferDesc = BackBufferTexture2D.Description;
                dxgiFormat = backBufferDesc.Format;

                // Check for render target size changes.
                Size 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.R16_Typeless,
                    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 | BindFlags.ShaderResource,
                    SampleDescription = new SharpDX.DXGI.SampleDescription(1, 0)
                };

                d3dDepthBuffer = new Texture2D(device, depthStencilDesc);
                if (d3dDepthBuffer != null)
                {
                    var depthStencilViewDesc = new DepthStencilViewDescription();
                    depthStencilViewDesc.Dimension = IsRenderingStereoscopic ? DepthStencilViewDimension.Texture2DArray : DepthStencilViewDimension.Texture2D;
                    depthStencilViewDesc.Texture2DArray.ArraySize = IsRenderingStereoscopic ? 2 : 0;
                    depthStencilViewDesc.Format = SharpDX.DXGI.Format.D16_UNorm;
                    d3dDepthStencilView         = this.ToDispose(new DepthStencilView(device, d3dDepthBuffer, depthStencilViewDesc));
                }
            }

            // Create the constant buffer, if needed.
            if (null == viewProjectionConstantBuffer)
            {
                // Create a constant buffer to store view and projection matrices for the camera.
                ViewProjectionConstantBuffer viewProjectionConstantBufferData = new ViewProjectionConstantBuffer();
                viewProjectionConstantBuffer = this.ToDispose(SharpDX.Direct3D11.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.
            HolographicStereoTransform cameraProjectionTransform = cameraPose.ProjectionTransform;

            // Get a container object with the view and projection matrices for the given
            // pose in the given coordinate system.
            HolographicStereoTransform?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.
            ViewProjectionConstantBuffer viewProjectionConstantBufferData = new ViewProjectionConstantBuffer();
            bool viewTransformAcquired = viewTransformContainer.HasValue;

            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.
                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;
            }
        }