NVIDIA RENDER INTERFACE (NRI)

NRI is a low-level abstract render interface which currently supports three backends: D3D11, D3D12 and Vulkan (VK). NRI has been designed to support all (at least major) low level features of D3D12 and VK APIs, but at the same time to simplify usage and reduce the amount of code needed (especially compared with VK). NRI is written in C++, but supports both C++ and C interfaces.

Goals:

• generalization of D3D12 (spec) and VK (spec) GAPIs
• providing access to low-level features of modern GAPIs
• low overhead
• explicitness
• D3D11 (spec) support (as much as possible)

Non-goals:

• high level RHI
• exposing entities not existing in GAPIs
• D3D11-like abstraction level
• hidden management of any kind

Key features:

• C++ and C compatible interfaces
• generalized common denominator for D3D12, VK and D3D11 GAPIs
• low overhead
• ray tracing support
• mesh shaders support
• D3D12 Ultimate features support, including enhanced barriers
• VK printf support
• validation layers (GAPI- and NRI- provided)
• default D3D11 behavior is changed to match D3D12/VK using NVAPI or AMD AGS libraries, where applicable
• supporting as much as possible VK-enabled platforms: Windows, Linux, MacOS, Android
• can be used as a shared or static library

Available interfaces:

• NRI.h - core functionality
• NRIDeviceCreation.h - device creation and related functionality
• NRIHelper.h - a collection of various helpers to ease use of the core interface
• NRILowLatency.h - low latency support (aka NVIDIA REFLEX)
• NRIMeshShader.h - mesh shaders
• NRIRayTracing.h - ray tracing
• NRIResourceAllocator.h - convenient creation of resources using AMD Virtual Memory Allocator, which get returned already bound to memory
• NRIStreamer.h - a convenient way to stream data into resources
• NRISwapChain.h - swap chain and related functionality

(some interfaces can be missing in the listing)

NRI is used in:

• NRI samples
• NRD Sample

C/C++ INTERFACE DIFFERENCES

C++	C
nri::Interface	NriInterface
nri::Enum::MEMBER	NriEnum_MEMBER
nri::CONST	NRI_CONST
nri::nriFunction	nriFunction
nri::Function	nriFunction
Reference &	Pointer *

ENTITIES

NRI	D3D11	D3D12	VK
Device	ID3D11Device	ID3D12Device	VkDevice
CommandBuffer	ID3D11DeviceContext (deferred)	ID3D12CommandList	VkCommandBuffer
CommandQueue	ID3D11DeviceContext (immediate)	ID3D12CommandQueue	VkQueue
Fence	ID3D11Fence	ID3D12Fence	VkSemaphore (timeline)
CommandAllocator	N/A	ID3D12CommandAllocator	VkCommandPool
Buffer	ID3D11Buffer	ID3D12Resource	VkBuffer
Texture	ID3D11Texture	ID3D12Resource	VkImage
Memory	N/A	ID3D12Heap	VkDeviceMemory
Descriptor	ID3D11*View	D3D12_CPU_DESCRIPTOR_HANDLE	Vk*View or VkSampler
DescriptorSet	N/A	N/A	VkDescriptorSet
DescriptorPool	N/A	ID3D12DescriptorHeap	VkDescriptorPool
PipelineLayout	N/A	ID3D12RootSignature	VkPipelineLayout
Pipeline	ID3D11*Shader and ID3D11*State	ID3D12StateObject	VkPipeline
AccelerationStructure	N/A	ID3D12Resource	VkAccelerationStructure

BUILD INSTRUCTIONS

• Install Cmake 3.15+
• Install on
  • Windows: latest WindowsSDK and VulkanSDK
  • Linux (x86-64): latest VulkanSDK and optional libx11-dev and libwayland-dev
  • Linux (aarch64): optional libx11-dev and libwayland-dev
• Build (variant 1) - using Git and CMake explicitly
  • Clone project and init submodules
  • Generate and build the project using CMake
• Build (variant 2) - by running scripts:
  • Run 1-Deploy
  • Run 2-Build

Notes:

• Xlib and Wayland can be both enabled
• Minimal supported client is Windows 8.1+. Windows 7 support requires minimal effort and can be added by request

CMAKE OPTIONS

• NRI_STATIC_LIBRARY - build NRI as a static library (off by default)
• NRI_ENABLE_VK_SUPPORT - enable VULKAN backend (on by default)
• NRI_ENABLE_D3D11_SUPPORT - enable D3D11 backend (on by default on Windows)
• NRI_ENABLE_D3D12_SUPPORT - enable D3D12 backend (on by default on Windows)

VK only:

• NRI_ENABLE_XLIB_SUPPORT - enable Xlib support (on by default)
• NRI_ENABLE_WAYLAND_SUPPORT - enable Wayland support (on by default)

D3D12 only:

• NRI_ENABLE_AGILITY_SDK_SUPPORT - enable Agility SDK (off by default)
• NRI_AGILITY_SDK_PATH - path to a directory containing Agility SDK: contents of .nupkg/build/native/ (C:/AgilitySDK by default)
• NRI_AGILITY_SDK_VERSION - Agility SDK version (614 or newer)
• NRI_AGILITY_SDK_DIR - directory where Agility SDK binaries will be copied to relative to CMAKE_RUNTIME_OUTPUT_DIRECTORY (AgilitySDK by default)

AGILITY SDK

Overview and Download sections can be found here.

D3D12 backend uses Agility SDK to get access to most recent D3D12 features. As soon as these features become available in the OS, installation of Agility SDK will be deprecated.

Installation steps:

• download Agility SDK package
  • preview versions require enabling Developer Mode in Windows
• rename .nupkg into .zip
• extract contents of .nupkg/build/native into NRI_AGILITY_SDK_PATH folder
  • can be located anywhere
• set NRI_AGILITY_SDK_DIR to a path, where bin folder needs to be copied
  • most likely closer to the executable
• set NRI_AGILITY_SDK_VERSION to the version of the package
• enable NRI_ENABLE_AGILITY_SDK_SUPPORT
• re-deploy project
• include auto-generated NRIAgilitySDK.h header in the code of your executable, using NRI

SAMPLES OVERVIEW

NRI samples can be found here.

Samples:

• DeviceInfo - queries and prints out information about device groups in the system
• Clear - minimal example of rendering using framebuffer clears only
• CTest - very simple example of C interface usage
• Triangle - simple textured triangle rendering
• SceneViewer - loading & rendering of meshes with materials
• BindlessSceneViewer - bindless GPU-driven rendering test
• Readback - getting data from the GPU back to the CPU
• AsyncCompute - demonstrates parallel execution of graphic and compute workloads
• MultiThreading - shows advantages of multi-threaded command buffer recording
• MultiGPU - multi GPU example
• RayTracingTriangle - simple triangle rendeing through ray tracing
• RayTracingBoxes - a more advanced ray tracing example with many BLASes in TLAS
• Wrapper - shows how to wrap native D3D11/D3D12/VK objects into NRI entities
• Resize - demonstrates window resize

LICENSE

NRI is licensed under the MIT License. This project includes NVAPI software. All uses of NVAPI software are governed by the license terms specified here.