NRD SAMPLE

NRD Sample is a high-performance playground and reference implementation for path tracing in games. It provides a comprehensive environment to see NRD (NVIDIA Real-time Denoisers) in action across all possible use cases and compare it directly with DLSS-RR. While NRD and DLSS-RR are highly competitive today, effective comparison requires enabling NRD "SH" mode (set via the NRD_MODE macro in Shared.hlsli). The sample is designed to demonstrate production-ready path tracing best practices suitable for real-time gaming that balance visual fidelity with high performance. A core focus of the project is high-performance glass and transparency rendering. Built on the NRI (NVIDIA Rendering Interface), the sample is natively cross-platform, supporting both D3D12 and Vulkan. The ideas from the sample are already used in several AAA games and game mods.

Features:

• best-in-class performance:
  • RTX 4080 @ 1440p (native) shows ~150 FPS at day time and ~110 FPS at night time in Bistro scene (when the importance sampling comes into play)
• fast path tracing based on Trace Ray Inline supporting:
  • tracing variants:
    • full resolution: probabilistic diffuse or specular lobe selection at the primary hit (recommended main use case)
    • half resolution: 0.5 diffuse ray + 0.5 specular ray (checkerboard rendering)
    • full resolution: 1 diffuse ray + 1 specular ray
  • material models:
    • "base color - metalness"
    • RTXCR hair and skin
  • smart levels of radiance caching, allowing to do only 1 bounce:
    • L1 radiance cache: previously denoised frame (essential for refractions)
    • L2 radiance cache: SHARC (global voxel-based cache)
  • simple and robust importance sampling scheme designed to work with generic emissive pixels, i.e. not analytical lights (not RESTIR)
  • realistic fast and robust glass with multi-bounce reflections and refractions not requiring denoising
  • several rays per pixel and bounces (mostly for comparison)
  • extremely fast implementation of Ray Cones for mip level calculation
  • curvature estimation
• NRD denoising:
  • simple integration based on NRD Integration layer
  • RELAX and REBLUR for radiance
  • SIGMA for sun shadows
  • Spherical Harmonics (Gaussians) mode essential for upscalers
  • history confidence bumping IQ of dynamic lighting to a new level
  • NRD debug validation layer
  • denoising best practices including hair denoising
  • occlusion-only modes
  • reference accumulation
  • NRD unit tests
  • NRD special tests
• native integration of DLSS-SR, DLSS-RR, FSR and XeSS via NRIUpscaler extension (not StreamLine)
• NOTE: don't forget to modify NRD_MODE in Shared.hlsli to SH to unclock Spherical Harmonics (Gaussians) resolve mode essential for image quality!

GitHub branches:

• "best practices" simplex branch
  • optimized for recommended usage (probabilistic split, HitDistanceReconstructionMode::AREA_3X3 reconstruction). Recommended for learning NRD integration and borrowing PT code. It offers better performance and has less code
• "all-in-one" main branch
  • contains every possible option and setting, used primarily for NRD development and maintenance.

HOW TO BUILD

• Install Cmake 3.30+
• Build (variant 1) - using Git and CMake explicitly
  • Clone project and init submodules
  • Generate and build project using CMake
  • To build the binary with static MSVC runtime, add -DCMAKE_MSVC_RUNTIME_LIBRARY="MultiThreaded$<$<CONFIG:Debug>:Debug>" parameter when deploying the project
• Build (variant 2) - by running scripts:
  • Run 1-Deploy
  • Run 2-Build

CMake options:

• USE_MINIMAL_DATA=OFF - download minimal resource package (90MB)
• RTXCR_INTEGRATION - use RTXCR for hair and skin rendering, download sample scene

HOW TO RUN

• Run 3-Run script and answer the cmdline questions to set the runtime parameters
• If Smart Command Line Arguments extension for Visual Studio is installed, all command line arguments will be loaded into corresponding window
• The executables can be found in _Bin. The executable loads resources from _Data, therefore please run the samples with working directory set to the project root folder (needed pieces of the command line can be found in 3-Run script)

Requirements:

• any GPU supporting "trace ray inline"

USAGE

By default, NRD is used in common mode. To switch to "SH" or "occlusion-only" modes, modify the NRD_MODE macro in Shared.hlsli to one of the following: NORMAL, OCCLUSION, SH, or DIRECTIONAL_OCCLUSION. RELAX doesn't support AO / SO denoising. If RELAX is the current denoiser, ambient term will be flat.

Controls:

• Right mouse button + W/S/A/D - move camera
• Mouse scroll - accelerate / decelerate
• F1 - toggle "gDebug" (can be useful for debugging and experiments)
• F2 - go to next test (only if TESTS section is unfolded)
• F3 - toggle emission
• Tab - UI toggle
• Space - animation toggle
• PgUp/PgDown - switch between denoisers