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Appeared on: Wednesday, November 12, 2008
Microsoft Releases Direct3D11 Preview

The November 2008 DirectX SDK released by Microsoft includes a preview of the Direct3D 11.

Direct3D 11 is an update to Direct3D 10.1 enabling new hardware features as well as improving the breadth of configurations supported by Direct3D. As such, Direct3D 11 enables developers to create applications and games that work on Direct3D 10, Direct3D 10.1, and Direct3D 11 hardware when it becomes available. With the addition of WARP and Direct3D 10 Level 9, Direct3D 10.1 and Direct3D 11 have the ability to target fast software rasterization and Direct3D 9 hardware.

This version of the Direct3D 11 technical preview includes support for the following:

Direct3D 11 provides additional pipeline stages to support real-time tessellation of high order primitives. With extensively programmable capabilities, this feature allows many different methods for evaluating high-order surfaces, including subdivision surfaces using approximation techniques, Bezier patches, adaptive tessellation, and displacement mapping. This feature will only be available on Direct3D 11-class hardware, so in order to evaluate this feature, developers need to use the Reference Rasterizer.

Compute Shader
The Compute Shader is an additional stage independent of the Direct3D 11 pipeline that enables general purpose computing on the GPU. In addition to all shader features provided by the unified shader core, the Compute Shader also supports scattered reads and writes to resources through Unordered Access Views, a shared memory pool within a group of executing threads, synchronization primitives, atomic operators, and many other advanced data-parallel features. A variant of the Direct3D 11 Compute Shader has been enabled in this release that can operate on Direct3D 10-class hardware. It is therefore possible to developing Compute Shaders on actual hardware, but an updated driver is required. The full functionality of the Direct3D 11 Compute Shader will is intended for support of Direct3D 11-class hardware, so in order to evaluate the full functionality, developers will need to use the Reference Rasterizer until such hardware is available.

Multithreaded Rendering
The key API difference from Direct3D 10 in Direct3D 11 is the addition of deferred contexts, which enables scalable execution of Direct3D commands distributed over multiple cores. A Deferred Context captures and assembles actions like state changes and draw submissions that can be executed on the actual device at a later time. By utilizing Deferred Contexts on multiple threads, an application can distribute the CPU overhead needed in the Direct3D11 runtime and the driver to multiple cores, enabling better use of an end-user's machine configuration. This feature is available for use on current Direct3D 10 hardware as well as the reference rasterizer.

Dynamic Shader Linkage
In order to address the combinatorial explosion problem seen in specializing shaders for performance, Direct3D 11 introduces a limited form of runtime shader linkage that allows for near-optimal shader specialization during execution of an application. This is achieved by specifying the implementations of specific functions in shader code when the shader is assigned to the pipeline, allowing the driver to inline native shader instructions quickly rather than forcing the driver to recompile the intermediate language into native instructions with the new configuration. Shader development is exposed through the introduction of classes and interfaces to HLSL.

Windows Advanced Rasterizer Platform (WARP)
Available in this SDK through Direct3D 11 and eventually also through Direct3D 10.1, WARP is a fast, multi-core scaling rasterizer that is fully Direct3D 10.1 compliant.

Direct3D 10 and Direct3D 11 on Direct3D 9 Hardware (D3D10 Level 9)
Available in this SDK through Direct3D 11 and eventually also through Direct3D 10.1, the Direct3D API can target most Direct3D 9 hardware as well as Direct3D 10, Direct3D 10.1 and Direct3D 11 hardware. This is achieved by providing the Feature Level mechanism, which groups hardware into six categories depending on functionality: 9_1, 9_2, 9_3, 10_0, 10_1 and 11_0. A card only meets a feature level if it is fully compliant to that level, and each level is a strict super-set of those below it. Functionality is minimally emulated to assure no unexpected performance cliffs are encountered. Thus, features like Geometry Shaders are not available for Direct3D 9 level targets.

Runtime Binaries
All runtime binaries provided in the Direct3D 11 tech preview that will be available on Windows 7 and Windows Vista SP1 are installed with the SDK and are labeled as "Beta" components (i.e. D3D11_beta.DLL). All beta-labeled components are time-bombed. To create projects to evaluate these new components, you must link to their equivalent beta-labeled import libraries (i.e. D3D11_beta.lib). If you have a PDC copy of Windows 7, the headers, libs, and pdbs provided in the Windows SDK with the build are appropriate for development using the Direct3D 11 components providing in Windows 7. Please reserve the use of the headers, libs, and pdbs in this SDK to the beta components provided herein.

D3DX11 current only supports texture loading functions for Direct3D 11 resources. In the future, this component will provide many of the technologies available in D3DX10 like a mesh container format as well as the Effects 11 system. An important difference between D3DX11 and D3DX10 is that D3DX11 does not contain shader compilation functionality. Instead this is provided directly through the D3D Compiler component, described below.

HLSL and Direct3D Compiler
The HLSL compiler has several new features for supporting the new technologies available in Direct3D 11. This includes object oriented programming through interfaces and classes, a direct indexing syntax for resource loads, and the 'precise' keyword for ensuring that all operations performed with a specific variable adhere to the strict floating point rules. Almost all new linguistic features have valid functionality on existing shader targets. In addition to supporting all Direct3D 9, Direct3D 10, Direct3D 10.1, and Direct3D 11 shaders the HLSL compiler also supports the special targets needed to write shaders for Direct3D 10 Level 9 targets. The D3D Compiler is now directly accessible outside of D3DX10 and D3DX11 through D3DCompiler.H and D3DCompiler.lib. With these new files, an application is not required to link to D3DX in order to perform runtime compilation, and an application is not required to include the compiler if only D3DX functionality is needed.

D3D11 Reference Rasterizer
The Reference Rasterizer provides a gold-standard rasterization implementation for evaluation of Direct3D 11 features not yet available in hardware. The Reference Rasterizer is also provided as a way to verify a specific hardware implementation's accuracy to the rasterization standard. The reference rasterizer is designed for correctness, not performance.

D3D11 SDK Layers
Direct3D11 SDK Layers provide a mechanism for tracking the operation of the Direct3D 11 runtime during development. Currently this is used for providing debug information, which not only includes errors on improper use but also warnings that recommend best practice use of the runtime and often provides in-depth, useful information for debugging.

This release has also four new samples that demonstrate D3D11.

The Dynamic Shader Linkage 11 sample demonstrates use of Shader Model 5 shader interfaces and Direct3D 11 support for linking shader interface methods at runtime.

The HDRToneMappingCS11 sample demonstrates how to setup and run the Compute Shader(CS for short later on), which is one of the most exciting new features of Direct3D 11. Although the sample only utilizes the CS to implement HDR tone-mapping, the concept should extend easily to other post-processing algorithms as well as more general calculations.

The MultithreadedRendering11 sample demonstrates how to split rendering among multiple threads, with very low overhead. The new SubD11 sample is very similar to the SubD10 sample in the DirectX SDK, except that it has been enhanced to take advantage of three new Direct3D 11 pipeline stages: the hull shader, the tessellator, and the domain shader.

In addition, there are four new samples that highlight tessellation, computer shaders, mulithreaded rendering, and dynamic shader linkage.

The complete DirectX SDK contains the DirectX Runtime and all DirectX software required to create DirectX compliant applications. It can beb downloaded here.

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