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NVIDIA RENDER INTERFACE (NRI)

NRI is a low-level abstract render interface, which has been designed to support all low level features of D3D12 and Vulkan GAPIs, but at the same time to simplify usage and reduce the amount of code needed (especially compared with VK).

Goals:

generalization of D3D12 (spec) and VK (spec) GAPIs
providing access to low-level features of modern GAPIs
providing high-level "quality of life" improving utilities, organized as extensions
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

Currently supported GAPIs:

Vulkan (VK)
D3D12
D3D11
None / dummy (everything is supported, but does nothing)

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 sample code:

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`	`ID3D11Shader` and `ID3D11State`	`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 rendering 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.