NVRHI

Introduction

NVRHI (NVIDIA Rendering Hardware Interface) is a library that implements a common abstraction layer over multiple graphics APIs (GAPIs): Direct3D 11, Direct3D 12, and Vulkan 1.2. It works on Windows (x64 only) and Linux (x64 and ARM64).

Key features:

• Automatic tracking of resource states and barrier placement (optional).
• Automatic tracking of resource usage and lifetime, deferred and safe resource destruction.
• Convenient and efficient resource binding model with little runtime overhead.
• Easy direct interaction with the underlying GAPI when necessary.
• Easy portability of the rendering code between the supported GAPIs.
• Hidden sub-allocation of upload buffers and versioning of constant buffers.
• Parallel command list recording and multi-queue rendering.
• Supports all types of pipelines: Graphics, Compute, Ray Tracing, and Meshlet.
• Validation layer and resource reflection for easy debugging.

Various early versions of NVRHI have been used in various projects created at NVIDIA, including:

• Asteroids demo
• DLSS SDK
• VRWorks
• VXGI
• WaveWorks

Requirements

• Windows or Linux (x64 or ARM64)
• CMake 3.10
• A C++ 17 compiler (Visual Studio 2019, GCC 8 or Clang 6)
• Windows SDK version 10.0.19041.0 or later for DX12 support

Building NVRHI

NVRHI can be configured to be used a set of static libraries in CMake-based projects, or as a single dynamic library.

To include NVRHI into a CMake project as static libraries:

1. Add this repository as a submodule.
2. Add a add_subdirectory(nvrhi) directive to the parent CMakeLists.txt.
3. Add dependencies to the necessary targets:
   • nvrhi for the interface headers, common utilities, and validation;
   • nvrhi_d3d11 for DX11 (enabled when NVRHI_WITH_DX11 is ON);
   • nvrhi_d3d12 for DX12 (enabled when NVRHI_WITH_DX12 is ON); and
   • nvrhi_vk for Vulkan (enabled when NVRHI_WITH_VULKAN is ON).

To build NVRHI as a shared library (DLL or .so):

1. Clone this repository recursively (including submodules).
2. Generate the project with CMake:
   • Set the NVRHI_BUILD_SHARED variable to ON.
   • Make sure to set the target platform to a 64-bit one. 32-bit builds are not supported.
3. Build and install as normal.

Using NVRHI in Applications

See the programming guide and the tutorial.

Shader Compiler

NVRHI includes an optional tool for compiling shaders and generating shader permutations. The shader compiler is normally built together with NVRHI when the NVRHI_WITH_SHADER_COMPILER variable is ON. It can be used from CMake rules by its target name shaderCompiler or directly from its install location using the executable name nvrhi-scomp.

The NVRHI shader compiler is just a front-end for DXC, it does not implement any shader language processing itself.

For the list of command line options, run nvrhi-scomp --help.

The shader compiler is driven by a configuration file that lists shaders, their targets and permutations. The file has one shader source per line, for example:

Shaders.hlsl -T vs_5_0 -E main_vs
Shaders.hlsl -T ps_5_0 -E main_ps -D ENABLE_SOMETHING={0,1}

The above configuration will compile 3 shaders total: one vertex shader main_vs and two permutations of pixel shader main_ps with different values of the ENABLE_SOMETHING define. The pixel shader permutations will be combined into a single permutation blob. Permutation blobs can be parsed using functions declared in <nvrhi/common/shader-blob.h>.

NVAPI Support

NVRHI includes optional support for certain DX11 and DX12 extensions available through the NVAPI library. The library is not distributed with NVRHI but is available separately here.

To enable NVAPI support, extract the NVAPI SDK into the nvapi subfolder of your main project and set the NVRHI_WITH_NVAPI CMake variable to ON.

The following extensions are supported:

• Fast Geometry Shader with optional coordinate swizzling (Maxwell+)
• Single Pass Stereo (Pascal+)
• HLSL Extensions through a fake UAV slot (see this blog post)

RTXMU Integration

NVRHI includes an optional integration of the RTXMU library. The library is included as a git submodule, and can be enabled with the NVRHI_WITH_RTXMU CMake variable.

When RTXMU integration is enabled, all bottom-level ray tracing acceleration structures (BLAS'es) are managed by that library. All built BLAS'es that have the AllowCompaction flag set are automatically compacted when ICommandList::compactBottomLevelAccelStructs method is called. No other configuration is necessary.

License

NVRHI is licensed under the MIT License.