Direct3D 12 Graphics Hardware Feature Levels

To handle the diversity of video cards in new and existing machines, Microsoft Direct3D 11 introduced the concept of feature levels. Each video card implements a certain level of Microsoft DirectX (DX) functionality depending on the graphics processing units (GPUs) installed. A feature level is a well defined set of GPU functionality. For instance, the 11_0 feature level implements the functionality that was implemented in Direct3D 11.

Now when you create a device, you can attempt to create a device for the feature level that you want to request. If the device creation works, that feature level exists, if not, the hardware does not support that feature level. You can either try to recreate a device at a lower feature level or you can choose to exit the application.

The basic properties of feature levels are:

• All Direct3D 12 drivers will be Feature Level 11.0 or better.
• A GPU that allows a device to be created meets or exceeds the functionality of that feature level.
• A feature level always includes the functionality of previous or lower feature levels.
• A feature level does not imply performance, only functionality. Performance is dependent on hardware implementation.
• A feature level is chosen when you call D3D12CreateDevice.
• For more detailed information on supported features (especially those marked Optional in the table below, which means that the hardware might support the feature but is not required to) call CheckFeatureSupport.

For information about limitations creating non-hardware type devices on certain feature levels, see Limitations Creating WARP and Reference Devices. For more information on the introduction of feature levels, refer to the Direct3D 11 documentation on Direct3D feature levels.

Numbering Systems

Hardware feature levels are not the same as API versions. For example, there is a D3D11.3 API, but there is no 11_3 hardware feature level. Feature levels are defined in the D3D_FEATURE_LEVEL enum.

There are three distinct numbering systems:

• Direct3D versions use a period; for example, Direct3D 12.0.
• Shader models use a period; for example, shader model 5.1.
• Feature levels use an underscore; for example, feature level 12_0

Feature Level Support

The following features are available for each Direct3D feature level.

The headings across the top row are Direct3D feature levels. The headings in the left-hand column are features.

• Requires the Direct3D 11.3 or Direct3D 12 runtime.
• Requires the Direct3D 11.1 runtime.
• Shader model 5.0 can optionally support double-precision shaders, extended double-precision shaders, the SAD4shader instruction, and partial-precision shaders. To determine the shader model 5.0 options that are available, call ID3D12Device::CheckFeatureSupport. Some compatibility depends on what hardware you are running on: Shader model 5.1 is only supported on hardware that supports the DirectX 12 API, regardless of the feature level that's being used. DirectX 11 hardware only supports up to shader model 5.0. The DirectX 12 API only goes down to feature level 11_0.
• Higher tiers are optional.
• Feature levels 12.0 and 12.1 require the Direct3D 11.3 or Direct3D 12 runtime.
• Feature level 11.1 requires the Direct3D 11.1 runtime.
• Feature level 11.0 requires the Direct3D 11.0 runtime

以上参数说明：
DirectX 11、12 API桌面窗口管理器（DWM）使用最大表面分辨率为16k，也就是说垂直或者水平的像素不能超过16384