RTX Character Rendering (RTXCR)

Introduction

RTX Character Rendering (RTXCR) implements techniques that are used for rendering realistic human hair and skin.

RTXCR implements two hair shading techniques, the traditional near-field Chiang BSDF [ Chiang15 ], and a novel far-field analytical approach developed by the Omniverse team. For more information on the that solution and how to integrate it, please check the RTXCR Hair Guide

RTXCR introduces a novel hair data structure called Linear-Swept Sphere (LSS). It delivers high performance in tracing and BVH updates while maintaining exceptionally low memory consumption. Additionally, it enables SOL tracing using the LSS Hardware Intersector on 4th-generation Ray Tracing Cores in Blackwell GPUs. For other RTX GPUs, we provide a fallback solution known as Disjoint Orthogonal Triangle Strips (DOTS), which replaces traditional triangle-based strands. For more details, check our LSS Technical Blog.

For skin, RTXCR implements a combined subsurface scattering solution which extended SOTA Burley Diffusion Profile [ Burley15 ] with a single scattering term. This provides better support for both backward scattering from diffusion profile and forward transmission from single scattering. For Technique Details and integration, check RTXCR SSS Guide

Project structure

Directory	Details
/docs	Documentation for showcased tech
/external	Helper dependencies and framework used for the samples
/assets	Assets and scene definitions
/samples	Samples showcasing usage of RTXCR
/libraries	Binaries, src, includes for RTXCR

Provided samples:

• Pathtracer (default): showcases the most commond use case - a pathtracer that relies on RTXCR to show the hair and skin techniques, including the hair BCSDF/BSSRDF evalution, importance sampling and denoising (DLSS-RR)

For more details of running sample, check RTXCR User Guide

Getting up and running

Prerequisites

RTX 20 series or newer. | Driver ≥ 572.16 | CMake v3.24.3 | Git LFS | Vulkan SDK 1.3.268.0 | Windows SDK ≥ 10.0.20348.0 (ShaderMake requirement)

Building and Running the Sample Apps

• To get started, clone the repository along with all submodules:

  • git clone --recursive https://github.com/NVIDIA-RTX/RTXCR.git

  If the repository was cloned without submodules, update them separately:

  • git submodule update --init --recursive

There are three ways to build and run the sample. Choose the method that best suits your workflow.

1. Building and Running with Scripts

If you only need to build and run the sample without modifying the code:

1. Run the build.bat script.

2. Once the build completes successfully, execute run.bat to launch the application.

2. Generating and Using a Visual Studio Solution

If you want to inspect or modify the code in Visual Studio:

1. Run the generateSolution.bat script. This will generate a Visual Studio solution and open it automatically.

2. We recommend selecting the RelWithDebInfo solution configuration and building the project in Visual Studio to achieve the best balance between performance and debugging capabilities.

3. Run the application from within Visual Studio.

3. Generating a Visual Studio Solution Using CMake GUI

If you prefer configuring the solution manually:

1. Assuming that the RTXCR SDK tree is located in D:\RTXCR, open CMake GUI and set the following parameters:

   • "Where is the source code" to D:\RTXCR
   • "Where to build the binaries" to D:\RTXCR\build

2. Click "Configure", set "Generator" to the Visual Studio you're using, set "Optional platform" to x64, click "Finish".

   • The data assets used for sample will be automatically downloaded to /assets folder in this step

3. Click "Generate", then "Open Project".

4. We recommend selecting the RelWithDebInfo solution configuration and building the project in Visual Studio to achieve the best balance between performance and debugging capabilities.

5. Open the RTXCR.sln in the /build folder.

6. Build and run the application using Visual Studio.

Contact

RTXCR is actively being developed. Please report any issues directly through the GitHub issue tracker, and for any information or suggestions contact us at [email protected]

Citation

If you use RTXCR in a research project leading to a publication, please cite the project.

BibTex:

@online{RTXCR,
   title   = {{{NVIDIA}}\textregistered{} {RTXCR}},
   author  = {{NVIDIA}},
   year    = 2025,
   url     = {https://github.com/NVIDIA-RTX/RTXCR},
   urldate = {2025-02-06},
}

License

See License.txt

Reference

[1]A practical and controllable hair and fur model for production path tracing, MJY Chiang, B Bitterli, C Tappan, B Burley Computer Graphics Forum 35 (2), 275-283 | Paper Link

[2]Approximate Reflectance Profiles for Efficient Subsurface Scattering. Per H. Christensen, B Burley.“An approximate reflectance profile for efficient subsurface scattering.” ACM SIGGRAPH (2015): 1-1 | Paper Link