Intel® Open VKL plugin for RenderMan*

The Intel® Open VKL plugin for RenderMan* implements the implicit field interface for Pixar's RenderMan. Through this plugin, applications can load OpenVDB files as Open VKL volumes, and gain both additional functionality and improved performance through use of Intel® Open Volume Kernel Library (Intel® Open VKL).

Building

Building the plugin requires Pixar's RenderMan, Open VKL, and OpenVDB.

Building Open VKL and OpenVDB

The Open VKL superbuild can be used to build Open VKL, OpenVDB, and their dependencies:

git clone https://github.com/openvkl/openvkl.git ./openvkl

mkdir openvkl_build
cd openvkl_build

cmake -D TBB_VERSION=2020.3 -D TBB_HASH="" \
  -D OPENVKL_EXTRA_OPTIONS="-DBUILD_EXAMPLES=OFF -DBUILD_TESTING=OFF" \
  ../openvkl/superbuild

cmake --build .

cd ..

After running the above, the installed components can be found in openvkl_build/install/.

Building the Plugin

The plugin requires a RenderMan installation to build. Set the environment as appropriate for your system, e.g.:

export RMANTREE=/opt/pixar/RenderManProServer-24.4

The other dependencies were already installed above. Set the environment so that CMake may find these via:

export CMAKE_PREFIX_PATH=${PWD}/openvkl_build/install

Now, build the plugin:

mkdir build
cd build

cmake -D OpenVDB_ROOT=${CMAKE_PREFIX_PATH} ..

cmake --build .

The plugins should now be built, including the primary Open VKL plugin (libprman_openvkl) and an auxiliary plugin used for benchmarking / comparison purposes (librif_benchmark).

Usage

Volume types

The plugin supports two Open VKL volume types which can be used with any imported VDB file:

• structuredRegular: a dense, regular grid
• vdb: a sparse grid, with internal representation similar to the OpenVDB data structure

The structuredRegular representation may provide improved performance, especially for small volumes; however its dense representation can require more memory. Conversely, the vdb representation is more memory efficient.

Additionally, the auto volume type may be used, which will choose the structuredRegular representation if the memory overhead is sufficiently small, and otherwise default to vdb. This feature is experimental.

Open VKL supports several additional volume types, but these are not exposed in the plugin at this time.

RIB file syntax

The plugin supports rendering of OpenVDB data as a volume. Three arguments are required: the VDB filename, the Open VKL volume type to use, and the grid name from the OpenVDB file to import. JSON arguments for density scaling (densityMult, densityRolloff) are optional. Primvars from additional OpenVDB grids can also be imported. Below are examples of the RIB file syntax.

Density field using VDB volume type

Volume "blobbydso:../build/plugins/openvkl/libprman_openvkl.so"
    [-40 40 -3 100 -40 40]
    [0 0 0]
    "constant string[3] blobbydso:stringargs" ["smoke.vdb" "vdb" "density"]
    "varying float density" []

Density field using structuredRegular volume type

Volume "blobbydso:../build/plugins/openvkl/libprman_openvkl.so"
    [-40 40 -3 100 -40 40]
    [0 0 0]
    "constant string[3] blobbydso:stringargs" ["smoke.vdb" "structuredRegular" "density"]
    "varying float density" []

Density field using VDB volume type, density scaling, and additional primvars

Volume "blobbydso:../build/plugins/openvkl/libprman_openvkl.so"
    [-6.881570 12.118430 -1.200000 59.700001 -7.939096 9.760904]
    [0 0 0]
    "constant string[4] blobbydso:stringargs" [
        "smoke2.vdb"
        "vdb"
        "density"
        "{\"densityMult\": 1.0,  \"densityRolloff\": 0.0}"]
    "varying float density" []
    "varying vector v" []

RIB filter plugin: rif_benchmark

A RIB filter plugin is also included, which can dynamically substitute which volume plugin is used, and for the Open VKL plugin also select the volume type used. The filter plugin assumes RIB files written for the impl_openvdb plugin syntax. Thus, this filter plugin can be used to conveniently render existing RIB files written for the impl_openvdb plugin with the Open VKL-based plugin, or for comparison purposes between different plugins and volume types.

Below are examples of how to use the RIB filter plugin, using RIB files included in the scenes/ directory. Note that the VDB data sets are not included in this repository; see the scenes/README.md for details.

Note that you may need to set your library search path for the dependencies built above. This can be done as:

export LD_LIBRARY_PATH=${PWD}/openvkl_build/install/lib:${LD_LIBRARY_PATH}

Rendering using the Open VKL plugin, VDB volume type

prman -rif ../build/plugins/rif_benchmark/librif_benchmark.so \
  -rifargs -plugin ../build/plugins/openvkl/libprman_openvkl.so -type vdb \
  -rifend -statsfile smoke_openvkl_vdb.xml \
  smoke.rib

Rendering using the Open VKL plugin, structuredRegular volume type

prman -rif ../build/plugins/rif_benchmark/librif_benchmark.so \
  -rifargs -plugin ../build/plugins/openvkl/libprman_openvkl.so -type structuredRegular \
  -rifend -statsfile smoke_openvkl_structuredRegular.xml \
  smoke.rib

Display filtering

The rif_benchmark plugin can also modify display outputs from the RIB file. These options, disabled by default, are:

• -filterDisplay: redirects display output to TIFF files, named according to the current volume plugin and volume type
• -it: enables interactive display (via the it tool) of rendering in progress

These options can be used in conjunction with the other arguments above, e.g.:

prman -rif ../build/plugins/rif_benchmark/librif_benchmark.so \
  -rifargs -plugin ../build/plugins/openvkl/libprman_openvkl.so -type vdb \
  -it \
  -rifend -statsfile smoke_openvkl_vdb.xml \
  smoke.rib

Known Issues

Below are currently known issues with this plugin. If you encounter any other issues, please create an issue on GitHub.

• Performance with aggregate volumes: the current OpenVKLImplicitField::Range() implementation may return value ranges that are conservatively large, which can result in more sampling than necessary when using RenderMan's aggregate volume functionality. We are working to improve this.