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OSPRay for Hydra

OSPRay interactive rendering plugin for USD Hydra

Rendering of the ALab scene using OSPRay for Hydra. The ALab asset is Copyright 2022 Animal Logic Pty Limited. All rights reserved.

OSPRay for Hydra

OSPRay for Hydra is an open source plugin for Pixar’s USD to extend the Hydra rendering framework with Intel® OSPRay. OSPRay for Hydra enables interactive, path traced rendering by utilizing OSPRay’s renderers and Intel® Open Image Denoise. OSPRay for Hydra and OSPRay are released under the permissive Apache 2.0 license.

As part of the Intel oneAPI Rendering Toolkit, OSPRay is highly-optimized for Intel® CPU architectures ranging from laptops to large-scale distributed HPC systems. OSPRay for Hydra leverages the Intel® Rendering Framework to deliver interactive rendering for large-scale models at high levels of fidelity, as demonstrated at SIGGRAPH 2018 using over 100GB of production assets.

Support and Contact

OSPRay for Hydra is still in beta, with new features and existing issues being worked on regularly. USD is also under active development and is often fast changing. We tag the OSPRay for Hydra releases to match specified USD releases, but cannot always anticipate all of the changes and resulting issues for users. Please report any issues you may run into to our issue tracker. We always welcome suggestions and especially pull requests!

Building OSPRay for Hydra

OSPRay for Hydra source is available on GitHub at OSPRay for Hydra. The master branch is typically the most stable branch and contains tagged releases.

Tags are of the form hdospray-vx.x.x-usdvx.x.x, with vx.x.x being the release of OSPRay for Hydra and usdv being the version of USD it is built against. This is required due to the frequently changing internals of hydra.

Currently OSPRay for Hydra is regularly tested on Ubuntu 22.04, and has been tested on Windows 10 and MacOS 13.6.


USD has a large number of dependencies depending on your configuration. We provide a superbuild for linux/mac which builds USD and other dependencies. At a base you will need the following system libraries, though you may need others depending on what USD modules you are building and what system you are running: - c/c++ compiler (gcc 6.3.1+)

  • cmake 3.1.1+ - (for USD python support including usdview) python (3.7.x+ recommended), with PySide2/PySide6, numpy, and PyOpenGL. ‘pip install PySide6 PyOpenGL’

If you are building standalone, you will need: - USD 23.02, 22.08, 21.08, or 20.08 - Other USD versions between these discrete releases may work, but are untested. - For a full list of USD dependencies, see the USD page. - OSPRay 3.0.0 - We recommend using ospray’s superbuild to build dependencies such as embree, ospcommon, and openvkl. OpenImageDenoise can also be enabled through superbuild. - rkcommon is a library dependency of OSPRay and hdOSPRay, and built as part of OSPRay’s superbuild.

Optional Dependencies

  • Houdini SDK (tested against 18.5, 19.0, 19.5). To use, enable SUPERBUILD_USE_HOUDINI in superbuild.
  • OpenImageDenoise
    • Open Image Denoise needs be be enabled in the OSPRay build.

Superbuild on Linux/MacOS

OSPRay for Hydra contains a cmake superbuild script that builds external dependencies for you and is the recommended way of building OSPRay for Hydra on Linux/Mac. Alternatively, instructions for manually building each component is also given. Currently, USD 23.02 is the default.

mkdir build
cd build
cmake -DCMAKE_INSTALL_PREFIX=<install_dir> ../scripts/superbuild/ (or use ccmake to specify option through gui)
cmake --build . -j <numthreads>

By default, all install files will be installed into /install. A setup script can then be called to set paths:

source <install_dir>/
usdview <usdfile> --renderer OSPRay

Manual Compiling USD on Linux/MacOS

To build USD, see the USD GitHub site. If you wish to use usdview, you must also enable imaging and python.
The options and compilers used can vary from our example, but make sure that TBB use is consistent across your build of USD, OSPRay for Hydra, and OSPRay. The command we use for building USD manually is:

python <USD_SOURCE>/build_scripts/ --python --usd-imaging --openimageio <USD_BUILD_DIR>

To set TBB explicitly, go to <USD_BUILD_DIR>/build/USD and set TBB libraries and include directories using cmake.

Compiling OSPRay on Linux/MacOS

You can use the distributed binaries of OSPRay or build it yourself. We recommend using the OSPRay superbuild system according the instructions listed on github. Make sure that TBB is the same used by USD. You can force using system TBB using the superbuild by going to <OSPRAY_BUILD_DIR>, and setting the cmake variable DOWNLOAD_TBB to OFF. GPU Support needs to be manually enabled, see OSPRay docs.

Compiling OSPRay for Hydra on Linux/MacOS

OSPRay for Hydra plugin uses a CMake build system which links in USD and builds externally from the USD source directory, but configures CMake as if it were inside the USD repository in order to build the plugin using USD internals. It must therefore be built against a version of USD that matches OSPRay for Hydra, which is specified in the versioning tag of OSPRay for Hydra.

  • Download/clone the git repo for OSPRay for Hydra

    $ git clone
  • Create a build directory and call CMake

    $ cd hdospray
    $ mkdir build
    $ cd build
    $ ccmake ..
  • Set CMAKE_INSTALL_PREFIX to the installation directory of USD.

  • Set pxr_DIR to the install directory of USD which contains pxrConfig.cmake

  • Set ospray_DIR to the directory containing your osprayConfig.cmake

    • This can be found in the root directory of the distributed binaries or if you are building and installing from source it can be found in <install>/lib/cmake/ospray-\*/
  • Set openvkl_DIR to install directory of OpenVKL. These will be the same as ospray_DIR if you downloaded the OSPRay binaries, or in OSPRay’s superbuild directory under install/openvkl/lib/cmake/openvkl*.

  • Set rkcommon_DIR to install directory of rkCommon. These will be the same as ospray_DIR if you downloaded the OSPRay binaries, or in OSPRay’s superbuild directory under install/rkcommon/lib/cmake/rkcommon*.

  • Set embree_DIR to install directory of Embree. These will be the same as ospray_DIR if you downloaded the OSPRay binaries, or in OSPRay’s superbuild directory under install/embree/lib/cmake/embree*.

  • Compile and install OSPRay for Hydra

    $ make -j install

The plugin should now be in <usd install directory>/plugin/usd/hdOSPRay

Compiling OSPRay for Hydra on Windows

Compliation on windows is similar to Linux/Mac.



Once built, the plugin should be located in your install directory under plugin/usd/HdOSPRay. A setup script is provided for setting env vars. If you built usd with usdimaging, you can run usdview <scenefile> and select view->Hydra and then Renderer->OSPRay.

Houdini setup is specific to each platform, but has been tested with Houdini 19.5.640. For Mac/Linux, there is a houdini_setup script in your Houdini installation directory. This should be sourced, and then source the script and you should be able to select OSPRay as a hydra delegate in the drop down menu in stage view. For windows, it is recommended to copy the bin and plugin directories from your hdOSPRay build to the respective directories in the Houdini install.

OSPRay can be set to the default renderer by either

  • Setting the HD_DEFAULT_RENDERER environment variable

  • Specifying --renderer OSPRay as a command line argument to usdview

Environment variables

Most of these options are also exposed through the usdview GUI under Hydra Settings.


    cpu (default) or gpu device.


    If built in, enable the denoiser


    Number of samples per pixel.


    Will progressively render frames until this many samples per pixel, then stop rendering.


    Set interactive scaling to match target fps when interacting. 0 Disables interactive scaling.


Number of light samples at every path intersection. A value of -1 leads to sampling all light sources in the scene. Does not affect scivis renderer.


    Number of ambient occlusion samples to compute per pixel. Does not affect path tracer.


    Globally modify the intensity of all lights.


    Use Monte Carlo path tracer instead of faster Whitted-style renderer.


    Maximum ray depth. Will affect the number of diffuse bounces as well as transparency.


    Use a simple diffuse + phone material instead of principled material.


    Specify arguments sent on to OSPRay for initialization. e.g. enable MPI.


    The type of pixel filter used by OSPRay: 0 (point), 1 (box), 2 (gauss), 3 (mitchell), and 4 (blackmanHarris).


    Force Quadrangulate meshes for debug.


  • Denoising using Open Image Denoise
  • Distributed multi-node rendering over MPI
  • UVTextures
  • Pixel Filters
  • usdLux lights: disk, distant, dome, quad, sphere.
  • Triangle meshes
  • Quad meshes
  • Subdivision surfaces
  • Ray traced shadows and ambient occlusion.
  • Path tracing
  • Physically-based materials
  • Principled shader (similar to Disney BSDF shader)

News, Updates, and Announcements

  • Oct 25, 2023: Version v1.0.0

    - USD 23.02 support
    - OSPRay 3.0
    - GPU support
    - Superbuild now part of core repo
    - Macosx and Windows build support
    - Fixes for Windows DLL loading
    - Houdini binary release builds
    - Resource loading now uses Hio
    - Openimageio dependency removal
    - Support for loading usdz files directly
    - Custom OSPRay materials
    - Changes to interactive rendering mode for smoother camera movement
    - Depth buffer transform to non-linear for DCC compositing
    - Various bug fixes
  • Jan 5, 2023: Version v0.11.0

    - Texture Transforms
    - UDIM textures
    - Texture channel masks
    - Tonemapper settings
    - Interactive rendering reworked
    - Bug fixes
  • Sep 20, 2022: Version v0.10.1

    - USD 22.08 support. 21.08 is still default in superbuild for houdini. 
    - Golden image tests added
    - Github actions workflow added for CI
    - Bug fixes
  • June 10, 2022: Version v0.10

    - USD 21.08 support, which is now the default in superbuild.  20.08 still supported if enabled.
    - Instance, Element, and Primitive ID buffers added
    - Testing added with image comparisons
    - Added facevarying texture and color support.
  • Feb 15, 2022: Version v0.9

    - Adding depth AOV
    - Adding normals AOV
    - Additional material parameters
    - Fixing generic texcoord naming
    - Update to OSPRay 2.9
    - Adding cylinder light
    - Adding camera depth of field
    - Minimal support for geomsubset materials
    - Ptex support currently deprecated in OSPRay.  Will be re-enabled upon OSPRay module_ptex release.
  • August 24, 2021: Version v0.8

    - Update to USD 20.08.
    - Houdini support.
    - Color buffer AOV support.
    - Superbuild script added.
    - Added camera light visibility flags.
    - Add thin materials.
  • May 28, 2021: Version v0.7

    - Update to OSPRay 2.6.0
    - Ptex support re-enabled.
    - Numerous light and material updates. Added disk lights.
    - Toggle for light enabled vs visible.
    - Animation update fixes.
    - Support for curves.
  • October 12, 2020: Version v0.6

    - Update to OSPRay 2.4.0
    - Added support for opacity textures.
    - Added adaptive view port scaling. The viewport is
      now scaled to reach a given interactive framerate (e.g., 10fps).
    - Fixed some bigs with animated shapes (e.g., ARKit data sets).
    - Added support to toggle the visibility of light sources and shapes.
  • July 31, 2020: Version v0.5

    • Update to OSPRay 2.2.0.
    • Added UsdLux light support.
    • Asynchronous rendering.
    • Dynamic resolution for greater interaction.
    • Pixel Filters.
    • Subdivision surfaces interpolation mode fixes.
  • June 15, 2020: Version v0.4

    • Update to OSPRay 2.1.0.
    • Update to USD 20.05.
  • September 15, 2019: Version v0.3

    • Subdivision surfaces support.
    • GUI options for usdview.
    • Various bug fixes.
  • April 30, 2019: Version v0.2.2

    • Various bug fixes.
    • OSPRay version updated to 1.8.5.
    • CMake targets.
    • Added animation support.
  • Mar 7, 2019: Version v0.2.1

    • Bug fixes.
    • Ptex updates.
    • Documentation.
  • Feb 28, 2019: Version v0.2.0

    • Initial Beta release version 0.2.0 is now available on the HdOSPRay GitHub page. This replaces the previous repository and versioning which was on my personal github account.