Introduction

VisRTX is a C++ rendering framework developed by the HPC Visualization Developer Technology team at NVIDIA.

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Key features

• Progressive forward pathtracing with next-event estimation and multiple importance sampling
• Hardware acceleration through NVIDIA OptiX (Multi GPU)
• Full MDL material support for physically-based BSDFs
• AI denoiser
• Triangle/sphere/cylinder/disk geometries
• Directional/sphere/quad/spot/ambient/HDRI area lights
• Perspective/orthographic cameras
• Depth of field
• Picking
• Tone mapping
• OpenGL interop
• Dynamic loading of VisRTX library
• Simple C++ interface

Please note that this is a research project and work in progress.

Installation

Supported Platforms

VisRTX is supported on both Linux and Windows.

Prerequisites

• CUDA 10 (Minimum: CUDA 8)
• OptiX 6 (Minimum: OptiX 5.1)
• MDL SDK 2019

Compile / Install

VisRTX requires a C++ compiler and uses the standard CMake compilation and installation procedure.

mkdir build && cd build
cmake PATH_TO_VISRTX
make
make install

Options

CMake Option	Description
VISRTX_USAGE_REPORT_VERBOSITY	Enables the usage report generated by OptiX. Possible values: 0/1/2/3.
VISRTX_USE_DEBUG_EXCEPTIONS	Compiles VisRTX and the underlying OptiX kernels with debug exception handling enabled.
VISRTX_BUILD_SAMPLE	Enables building of the sample applications.
VISRTX_SAMPLE_USE_DYNAMIC_LOADING	Use dynamic loading rather than dynamic linking in the samples to load VisRTX.
VISRTX_SAMPLE_WITH_GLFW	Enables GLFW-based OpenGL windows with GUI in the samples.
VISRTX_SAMPLE_WITH_EGL	Enables EGL-based OpenGL offscreen interop in the samples (Linux only).

Compiling on Windows using Visual Studio 2017

On Windows, VisRTX can be compiled using Visual Studio's built-in CMake support.

Just place a CMakeSettings.json file with the following contents (adjust paths accordingly) next to VisRTX's CMakeLists.txt:

{
  "configurations": [
    {
      "name": "x64-Release",
      "generator": "Ninja",
      "configurationType": "Release",
      "inheritEnvironments": [
        "msvc_x64_x64"
      ],
      "buildRoot": "C:\\.build\\VisRTX\\${name}",
      "installRoot": "C:\\.install\\VisRTX",
      "cmakeCommandArgs": "",
      "buildCommandArgs": "-v",
      "ctestCommandArgs": "",
      "variables": [
        { "name": "OptiX_INSTALL_DIR", "value": "C:\\PATH\\TO\\OptiX-SDK-6.0.0" },
        { "name": "MDL_INSTALL_DIR", "value": "C:\\PATH\\TO\\mdl-sdk-314800.830" },
        { "name": "VISRTX_BUILD_SAMPLE", "value": "ON" },
        { "name": "VISRTX_SAMPLE_USE_DYNAMIC_LOADING", "value": "ON" },
        { "name": "VISRTX_USAGE_REPORT_VERBOSITY", "value": "0" },
        { "name": "VISRTX_USE_DEBUG_EXCEPTIONS", "value": "OFF" }
      ]
    }
  ]
}

Examples

Several example applications are included showcasing and verifying the features of VisRTX.

The visRtxSampleBasic application combines most features of VisRTX in a single test bed using the general-purpose basic material, and has the optional parameters: benchmark, offscreen, egl, dump.

The visRtxSampleMeshViewer can be used to load a set of arbitrary OBJ meshes and apply MDL materials to them. visRtxSampleMDL loads a single mesh and renders multiple instances with various MDL materials.

Nested volumetric materials are demonstrated in visRtxSampleVolume.

The samples include a set of MDL material definitions based on the most common OSPRay materials with a similar parameter interface. These include ::OBJMaterial, ::CarPaint, ::Principled, ::Metal, ::Alloy, ::Glass, ::ThinGlass, ::MetallicPaint, and can be found in sample/data/ospray.mdl.

Example command line: ./visRtxSampleMeshViewer ::OBJMaterial cow.obj ::CarPaint car.obj ::MetallicPaint --plane

The samples can be easily changed to load MDL files and resources from disk, or switch from instance to class compilation.

Documentation

There is no official documentation yet, sorry!

The VisRTX.h header gives a concise overview of the API.

Most of the provided functionality is demonstrated in the included sample applications. See sample/Sample.h for basic framework setup.

Please note that this project is work in progress and the API as well as features can change.

Environment Variables

Some performance-relevant properties of the renderer can be overridden using the following environment variables, so an existing application can be tuned without recompilation.

Environment Variable	Values
VISRTX_DEVICES	list of int, e.g., 0, 1, 0,1
VISRTX_MIN_BOUNCES	int > 0
VISRTX_MAX_BOUNCES	int > 0
VISRTX_EPSILON	float >= 0
VISRTX_CLAMP_DIRECT	float >= 0
VISRTX_CLAMP_INDIRECT	float >= 0
VISRTX_TONE_MAPPING	0/1
VISRTX_DENOISER	0/1
VISRTX_SAMPLE_ALL_LIGHTS	0/1

MDL

For more advanced materials check out vMaterials, a curated collection of free-to-use MDL materials representing common real world materials used in Design and AEC workflows.

The MDL wrapper provided by VisRTX is self-contained and can be of interest to anyone who wants to access the MDL SDK from an OptiX-based application.

Features

• Class and instance compilation
• Load MDL from memory and disk (including texture resources)
• Update parameters (and recompile if necessary)
• Arbitrary OptiX samplers as parameters

Multi-GPU

VisRTX automatically makes use multiple GPUs if available.

For best OpenGL interop performance, make sure to enable Maximize 3D performance in the SLI configuration. It is also worthwhile to experiment with the CUDA device order, which can have a noticeable impact on the interop performance. For instance, in a dual GPU setup make sure to give CUDA_VISIBLE_DEVICES='1,0' a try!

Feedback

Feedback, issues and pull requests welcome!

We would love to hear more about your use cases of VisRTX!

If you have any questions, feature requests, issues, or ideas for improvement, please feel free to reach out at [email protected].