Interpretation of X Channel
This section applies only to Windows 7 and later operating systems.
The user-mode display driver should read the X channel in all formats that include X (for example, DXGI_FORMAT_B8G8R8X8_UNORM) as 1.0f when such formats are presented to filtering hardware or the blender.
The X channel must be copied unmodified when data is moved outside of the 3-D pipeline (that is, when an application calls the ID3D10Device::CopyResource, ID3D10Device::CopySubresourceRegion, or ID3D10Device::UpdateSubResource method). For more information about these methods, see the DirectX SDK documentation.
Build date: 1/22/2014