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OpenVDB
Developers	DreamWorks Animation, Academy Software Foundation
Initial release	August 3, 2012; 13 years ago (2012-08-03)

Stable release	13.0.0^[1] / 4 November 2025; 3 months ago (4 November 2025)

Written in	C++
Type	Software library
License	Mozilla Public License 2.0
Website	openvdb.org
Repository	github.com/AcademySoftwareFoundation/openvdb

OpenVDB is an open source software library for working with sparse volumetric data. It provides a hierarchical data structure and related functions to help with calculating volumetric effects in CGI applications. Volumetric effects apply to volumes, as opposed to just on surfaces. An example is fog.

Specifically catering for feature film production, the library was originally developed by DreamWorks Animation and is currently maintained by the Academy Software Foundation (ASWF). The primary authors are Ken Museth, Peter Cucka, Mihai Aldén, and David Hill. OpenVDB is written in C++ and has Python bindings.

OpenVDB is supported in a wide range of CGI software, such as Blender (since April 2016), Cinema 4D, Houdini, and RenderMan. It was first used in the films Puss in Boots (2011)^[2] and Rise of the Guardians (2012).

What does VDB stand for?

[edit]

Over the years VDB has been interpreted to mean different things, none of which are very descriptive: "Voxel Data Base", "Volumetric Data Blocks", "Volumetric Dynamic B+tree", etc. In early presentations of VDB even a different name was used, "DB+Grid", which was abandoned to emphasize its distinction from similarly named, but different, existing sparse data structures like DT-Grid or DB-Grid. The simple truth is that "VDB" is just a name.^[3]^[4]

References

[edit]

^ "Release 13.0.0". 4 November 2025. Retrieved 6 November 2025.
^ "DreamWorks Animation Releases Proprietary Volumetric Format OpenVDB to Open Source Community" (PDF).
^ "OpenVDB Frequently Asked Questions". Retrieved 2022-02-24.
^ "CppCast Episode 227: OpenVDB with Ken Museth". YouTube. Retrieved 2023-08-16.

External links

[edit]

Official website
openvdb on GitHub

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OpenVDB is an open-source C++ library that implements a novel hierarchical data structure and a suite of tools for the efficient storage, compression, and manipulation of sparse, time-varying volumetric data on 3D voxel grids.^[1] Developed initially at DreamWorks Animation for volumetric effects in feature film production, it enables fast random access to voxels with constant-time performance, making it ideal for large-scale simulations and rendering tasks in computer graphics.^[2] The library's development began in 2007 under the leadership of Ken Museth, evolving through internal tools like DB-Grid and VDB before being released as open-source software in August 2012.^[2] In 2018, governance and maintenance transitioned to the Academy Software Foundation (ASWF), an organization backed by the Academy of Motion Picture Arts and Sciences and the Linux Foundation, ensuring sustained community-driven evolution.^[2] Key contributors have included Peter Cucka, Mihai Aldén, David Hill, and teams from studios like DNEG and NVIDIA, who have added features such as particle support (OpenVDB Points in 2016), a high-level shading language (OpenVDB AX in 2018), GPU-optimized variants (NanoVDB in 2020), and interfaces like OpenVDBLink for Mathematica (2022). Recent developments as of 2025 include the release of OpenVDB 12.1.0 in August, enhancing GPU tools and performance.^[3] OpenVDB has earned multiple Academy Scientific and Technical Awards for its innovations: a Technical Achievement Award in 2014 to Museth, Cucka, and Aldén for its creation, and a Scientific and Engineering Award in 2024 to Museth, Cucka, and Aldén for its ongoing impact in the motion picture industry, alongside a Technical Achievement Award to Jeff Lait, Dan Bailey, and Nick Avramoussis for its continued feature expansions.^[4] Its core strengths include support for various grid types (e.g., level sets, fog volumes, and vector grids), advanced operations like morphological and topological processing, mathematical transforms, and integration with rendering pipelines, all while handling massive datasets that traditional dense arrays cannot efficiently manage.^[5] Widely adopted in visual effects pipelines at studios like DreamWorks, Industrial Light & Magic, and Weta Digital, OpenVDB also extends to real-time applications, scientific simulations, and tools like Houdini and Blender through bindings in Python and other languages, with recent enhancements in Blender's Geometry Nodes for volume processing as of October 2025.^[2]^[6]

Overview

Definition and Purpose

OpenVDB is an open-source C++ library designed for the efficient storage and manipulation of sparse, volumetric data discretized on three-dimensional grids, employing a hierarchical data structure particularly suited for level-set representations.^[2]^[7] Developed initially at DreamWorks Animation, it provides a suite of tools for handling high-resolution, time-varying volumes while supporting dynamic topology changes.^[2] The primary purpose of OpenVDB is to enable memory-efficient representations of 3D voxel grids in applications requiring large-scale simulations and rendering, such as visual effects (VFX) production, where traditional dense grids become computationally and storage-prohibitive due to their uniform allocation of memory across empty space.^[2]^[7] By focusing on sparsity, it facilitates operations like numerical simulations, compositing, and voxelization without the overhead of fully populated arrays, making it indispensable for industry workflows involving complex phenomena like fluids, smoke, and clouds.^[5] The acronym VDB stands for "Voxel Data Base," highlighting its database-like organization for managing voxel data hierarchically.^[8] Key benefits include a dramatically reduced memory footprint for sparse data—for instance, storing data equivalent to 228 million voxels in approximately 1 GB, compared to 14 TB for a dense grid of similar effective resolution—and constant-time random access to individual voxels.^[7] This efficiency stems from its sparse hierarchical node structure, which allocates storage only where data is present.^[2]

Core Principles

OpenVDB's design is fundamentally driven by the principle of sparsity, which addresses the inefficiency of traditional dense volumetric representations in handling large-scale 3D data with vast empty regions. By storing only non-zero or active voxels—those containing meaningful values—OpenVDB minimizes memory usage while enabling efficient manipulation of high-resolution volumes that would otherwise require prohibitive resources. This approach is particularly suited for sparse data sampled at high spatial frequencies, such as those encountered in visual effects simulations, where empty space dominates the domain.^[5]^[9] At the heart of this sparsity is a hierarchical organization based on a multi-level tree structure, typically comprising a root node, internal nodes, and leaf nodes arranged in fixed depths to achieve logarithmic access times. The root and internal nodes manage coarser representations of the volume using sparse indexing mechanisms, while leaf nodes store dense arrays of fine-grained voxel data. This B-tree-like hierarchy ensures cache-coherent, near-constant-time random access to any voxel, regardless of the grid's overall size, by traversing only the relevant branches of the tree.^[5]^[9] A key application of these principles lies in the representation of level sets and signed distance fields (SDFs), which implicitly define surfaces through the distance from the nearest surface point, with positive values outside and negative inside the surface. OpenVDB stores these as narrow-band level sets, confining active voxels to a thin band around the surface (typically three voxels wide) to exploit sparsity, while inactive regions are represented by constant background values. This enables efficient implicit surface modeling with dynamic topology changes, such as those during fluid simulations.^[5]^[9] OpenVDB further distinguishes itself by supporting both bounded and unbounded grids, allowing representation of infinite domains through adaptive refinement without fixed spatial limits. Unbounded grids leverage the hierarchical tree to extend dynamically into index space, constrained only by coordinate precision (e.g., 32-bit integers), while bounded variants map to finite world spaces via affine transforms. This flexibility accommodates diverse applications, from localized effects to expansive environments.^[5]^[9]

History and Development

Origins and Initial Release

OpenVDB originated at DreamWorks Animation, where it was developed to overcome memory and performance limitations in processing large-scale volumetric effects, such as smoke, fire, and water simulations, which are common in feature film production.^[10] The project addressed the challenges of handling sparse, high-resolution voxel data that traditional dense grid formats struggled with, enabling more efficient storage and manipulation for visual effects pipelines.^[11] This need was particularly driven by the demands of animated films requiring dynamic topology changes in volumetric elements, as seen in productions like Puss in Boots (2011) and Madagascar 3: Europe's Most Wanted (2012).^[12] The primary creator was Dr. Ken Museth, a principal research lead at DreamWorks Animation, who led the development alongside key contributors including Peter Cucka, Mihai Aldén, and David Hill.^[2] Museth's work built on earlier research into sparse volume representations, motivated by the growing complexity of volumetric simulations in films like How to Train Your Dragon 2 (2014), where expansive effects demanded scalable data structures.^[11] The team's goal was to create a hierarchical data structure that provided compact storage, fast random access, and support for time-varying data, while fostering interoperability across VFX tools to move away from proprietary formats.^[12] OpenVDB was first released to the open-source community on August 3, 2012, under a custom DreamWorks open-source license that encouraged adoption in the VFX industry.^[2] This initial version emphasized tools for level set representations and sparse volumetric processing, aiming to standardize data interchange in production pipelines and enable broader collaboration.^[12] The project later transitioned to more permissive governance under the Academy Software Foundation in 2018, enhancing its accessibility and long-term maintenance.^[2]

Major Milestones and Versions

OpenVDB achieved early adoption milestones shortly after its open-source release in 2012, with integration into SideFX Houdini version 13 in November 2013, allowing artists to leverage its sparse volumetric tools directly within the software's node-based workflow.^[13] This facilitated its uptake in production environments, including by leading visual effects studios such as Industrial Light & Magic (ILM) and Weta Digital, where it became essential for simulating and rendering complex effects like fluids and smoke in feature films.^[14] Version 3.0, released in January 2015, marked a significant technical advancement by introducing multi-threaded operations in core tools such as prune, signedFloodFill, changeBackground, and LevelSetTracker methods, enabling scalable processing of large datasets on multi-core systems.^[15] It also added delayed loading for .vdb files to reduce memory usage during I/O and incorporated Blosc LZ4 compression.^[3] In August 2018, OpenVDB transitioned governance from DreamWorks Animation to the Academy Software Foundation (ASWF), the first project hosted by this Linux Foundation-backed organization, which broadened collaboration across the VFX industry.^[2] Subsequent releases built on this foundation, with version 6.0 in December 2018 providing performance optimizations for mesh-to-volume conversion and point data handling, alongside improvements to tools for point grids.^[3] Version 7.1.0 in August 2020 introduced the FastSweeping class for signed distance fields and SDF/fog conversion tools.^[3] Version 9.0 in October 2021 integrated NanoVDB, a GPU-optimized variant supporting CUDA for accelerated rendering and computation on NVIDIA hardware, while version 10.0 in October 2022 extended this with tools like OpenVDBLink for Mathematica integration and further ValueAccessor performance gains.^[16]^[17] Updates in version 11.0, released in November 2023, improved Python bindings with expanded support for point data modification and tree hierarchy access, simplifying scripting and integration in diverse workflows.^[3] To further encourage community contributions, OpenVDB relicensed from the Mozilla Public License 2.0 to Apache 2.0 with version 12.0 in October 2024, aligning with ASWF standards for permissive use and redistribution.^[18] As of November 2025, subsequent minor releases included version 12.1.0 in August 2025, which added new level set constructors such as createLevelSetCapsule, and version 13.0.0 on November 3, 2025, introducing Half Grid support and enhancements to NanoVDB for dynamic topology.^[3]

Technical Architecture

Sparse Hierarchical Data Structure

OpenVDB employs a sparse hierarchical data structure based on a B-tree-like architecture to efficiently represent volumetric data, where the root node serves as the top-level index for the entire volume and subdivides the index space into 3D child nodes.^[5] This root node has no fixed size limit and uses a dynamic table to manage child nodes, enabling scalable storage for large volumes while only allocating nodes for regions containing relevant data.^[19] The structure achieves adaptive resolution by refining detail only in areas with non-zero or active data, utilizing a three-level hierarchy beneath the root: the first internal level covers blocks of 32³ voxels per node, the second internal level covers 16³ voxels per node, and leaf nodes store 8³ voxels each.^[5] This configuration, with log₂ dimensions of 5, 4, and 3 for the internal and leaf levels respectively, allows for high-resolution sampling in sparse regions without wasting memory on empty space, as inactive tiles propagate constant values down the tree.^[5] Access to individual voxels occurs through traversal of this hierarchy, yielding constant time complexity of O(1) due to the fixed tree depth and efficient node lookup mechanisms.^[5] Value accessors facilitate cached, bottom-up traversal for rapid queries, while thread-safe alternatives ensure concurrent access without caching overhead.^[8] The data structure supports multiple data types through templated grids, including FloatGrid for scalar densities, Vec3SGrid for short vector fields like velocities, and BoolGrid for boolean masks, all sharing the same hierarchical framework.^[5] Compression techniques, such as bitmasks for active states and quantized values in nodes, further optimize storage but are applied at the node level without altering the core hierarchy.^[5]

Node Types and Levels

OpenVDB employs a multi-level hierarchical tree structure composed of distinct node types that enable efficient sparse representation of volumetric data. The tree typically consists of a root node at the highest level, one or more levels of internal nodes, and leaf nodes at the lowest level. Each node type serves a specific role in indexing and storing data, with the hierarchy designed to balance memory efficiency and access speed. The default configuration uses four levels, where the log2 dimensions of nodes are parameterized as 5 for the upper internal level, 4 for the lower internal level, and 3 for the leaf level, corresponding to table sizes of 32×32×32, 16×16×16, and 8×8×8 respectively.^[5] Leaf nodes, positioned at level 0, store the actual voxel data in a dense 8×8×8 grid, where each voxel holds a value and an active state. These nodes encode voxel topology using a bitmask for active/inactive states and store values in a dense direct access table (buffer) of 512 entries, one for each voxel in the 8×8×8 grid. While memory is allocated for all voxels in an existing leaf node, inactive voxels return the background value on access, and overall sparsity is maintained by allocating leaf nodes only in regions with active data. Internal nodes, at levels 1 and 2 in the default setup, act as branching indices, each maintaining a fixed-size table of pointers to child nodes or uniform tile values for unoccupied regions; for instance, a level 1 internal node indexes 16×16×16 possible child leaf nodes or tiles. The root node, at the highest level (level 3 by default), is a specialized internal node without a fixed table size, instead using a hash map to manage pointers to its child internal nodes, effectively defining the global index space without imposing hard bounds.^[5]^[7] The hierarchy supports active and inactive states not only at the voxel level but also propagating upward: a node is considered empty (and can be pruned) if all its descendants are inactive or uniform, replacing the subtree with a single tile value to maintain sparsity. This mechanism ensures that only regions with meaningful data are allocated, with tools like the prune method optimizing the tree by removing such inactive branches. Levels and node dimensions are configurable through C++ template parameters, such as in tree::Tree4<ValueType, Log2Dim1, Log2Dim2, Log2Dim3>, allowing users to adjust branching factors for different resolutions or performance needs, though the default is optimized for typical visual effects workflows.^[5] Leaf nodes optionally support multiple buffer layers within their value tables to facilitate operations like numerical time integration, where separate buffers store voxel states at different timesteps—for example, three buffers for a third-order Runge-Kutta scheme in advection simulations—without requiring additional node allocation. This buffering aids boundary handling in dynamic simulations by preserving temporal data locally, though it does not introduce explicit padding beyond the fixed 8×8×8 extent.^[7]

Storage and Compression Mechanisms

OpenVDB employs a combination of hierarchical sparsity and specialized compression techniques to minimize memory usage for volumetric data, particularly in scenarios with large empty regions typical of visual effects and simulations. The core storage relies on bitmasks within nodes to encode active topology efficiently, avoiding allocation for inactive voxels, while additional codecs handle value data. These mechanisms enable substantial reductions in both in-memory footprint and on-disk size, with the sparse structure alone providing orders-of-magnitude savings for datasets where active voxels constitute a small fraction of the total volume.^[7] For leaf nodes, which store the finest-level 8×8×8 voxel grids, Blosc compression is applied to the value buffers containing floating-point data, offering faster encoding and decoding than traditional ZIP while achieving competitive ratios for sparse floats. Blosc operates by chunking data and applying a combination of shuffling, bitshuffle, and LZ4 or Zstd compression, tailored for numerical arrays, and is enabled via the COMPRESS_BLOSC flag during file I/O. In practice, this yields significant size reductions for sparse datasets, with reported improvements in compression ratios and write times through larger block sizes in recent versions.^[20]^[3] OpenVDB distinguishes between topology-only and full compression modes to suit different use cases. Topology-only storage, activated via the COMPRESS_ACTIVE_MASK option, encodes solely the bitmask of active voxels (a 64-bit or 512-bit structure per node indicating which child tiles or voxels are present), omitting value data entirely; this is ideal for applications focused on surface extraction or boolean operations where values can be reconstructed later. Full compression extends this by including compressed value arrays for active elements, using Blosc or ZIP on the buffer of non-uniform values, while uniform tiles are represented by a single scalar to exploit spatial coherence. The bitmask approach alone provides lossless topology compression, with further gains from value codecs in full mode, as demonstrated in early VDB implementations where combining bitmasks with Deflate reduced file sizes by 13-25% beyond sparsity alone.^[20]^[7] Quantization further optimizes storage by reducing precision for auxiliary data channels, such as velocities or attributes, where full 32-bit floating-point accuracy is unnecessary. The RealToHalf mapping truncates values to 16-bit half-floats during serialization, halving the per-voxel size without altering the tree topology, and is particularly effective for secondary grids in simulations; this can be combined with Blosc for compounded savings, though it introduces minor lossiness.^[20] The .vdb file format encapsulates these mechanisms in a custom binary structure, beginning with a header containing a magic number, version identifiers, and a unique UUID for versioning and integrity. Metadata, such as grid names, active voxel counts, and bounding boxes, precedes the serialized grids, which are stored as trees with optional instancing to avoid duplication of shared content; compression flags and offsets enable random access and partial loading. This design supports both in-core and out-of-core workflows, with grids written in a self-describing manner akin to hierarchical containers, though it is a proprietary format optimized for volumetric data rather than a general-purpose library like HDF5.^[21]

Operations and APIs

Data Access and Iteration

OpenVDB provides efficient mechanisms for accessing and iterating over voxel data within its sparse grids, leveraging the hierarchical structure to minimize unnecessary traversals of empty regions. Data access is primarily achieved through the ValueAccessor class, which enables fast random lookups of voxel values at specific integer coordinates in index space, achieving up to three times the performance of direct tree access by caching traversal paths from common ancestors.^[5] This accessor supports both read-only and read-write operations, with thread-safe variants available for concurrent modifications, though the latter incurs overhead from internal locking.^[5] Iteration over grid data is facilitated by specialized iterators that respect the sparse topology, ensuring constant-time complexity per active voxel. The ValueAllIter provides read/write access to all voxels and tiles within a leaf node, including inactive ones, allowing comprehensive traversal without skipping background values.^[5] In contrast, the ValueOnIter iterates solely over active (non-background) values across the entire tree or grid, enabling efficient processing of sparse data by visiting only the populated regions in O(1) time per active voxel.^[5] These iterators use a test() method to check for completion rather than conforming to standard STL interfaces, optimizing for the hierarchical nature of the data structure as described in the foundational OpenVDB design.^[9] Coordinates in OpenVDB operate in two primary spaces to balance discrete addressing with continuous spatial queries. Index space employs unit-less integer coordinates (i, j, k) to directly reference voxels, with a continuous extension for sub-voxel interpolation during operations like sampling.^[5] World space, in turn, provides physical context by transforming index coordinates via a grid-embedded Transform object, which maps between the two spaces using methods such as indexToWorld and supports affine and nonlinear mappings for applications requiring real-world positioning.^[22] For local neighborhood queries, OpenVDB's ValueAccessor supports efficient access to the 26-connected neighbors (face, edge, and vertex adjacent voxels) in 3D without loading the entire grid, by exploiting inverted traversal from shared ancestor nodes to retrieve values in constant time relative to the local density.^[5] This approach is particularly advantageous for sparse volumes, where full grid loading would be prohibitive, and aligns with the structure's design for high-resolution data.^[9] To leverage multi-core processors, OpenVDB supports parallel iteration through integration with OpenMP, allowing multiple threads to concurrently process disjoint portions of the grid using independent ValueAccessor instances for read-only access, thereby scaling performance linearly with core count on active voxel workloads.^[5]

Mathematical Operations

OpenVDB provides a suite of built-in mathematical operations for processing sparse volumetric data, particularly focused on level set representations using signed distance functions (SDFs). These operations leverage the library's hierarchical structure to efficiently handle large-scale computations while preserving sparsity. Key algorithms include constructive solid geometry (CSG) operations for combining level sets, filtering techniques for smoothing, advection methods for dynamic simulations, and topology optimization tools to refine the data structure post-processing.^[23] Level set operations in OpenVDB support CSG primitives such as union, intersection, and subtraction (difference) on SDF grids. The union of two level sets

\phi_A

and

\phi_B

is computed as

\phi_{A \cup B} = \min(\phi_A, \phi_B)

, the intersection as

\phi_{A \cap B} = \max(\phi_A, \phi_B)

, and the subtraction as

\phi_{A \setminus B} = \max(\phi_A, -\phi_B)

. These are implemented via threaded, sparse traversal functions in the tools::csgUnion, tools::csgIntersection, and tools::csgDifference utilities, which modify the input grid in place for efficiency and require deep copies of inputs to avoid data loss. While fast marching methods are referenced in the library's level set filtering for reinitialization and interface tracking (drawing from Sethian's foundational work on level set methods), the CSG operations themselves rely on direct min-max evaluations rather than explicit marching solvers.^[23]^[24] Filtering operations enable smoothing of level set densities and surfaces, with built-in support for Gaussian blur and Laplacian diffusion. The Gaussian filter approximates a 3D Gaussian kernel

G(\mathbf{x}) = \frac{1}{(\sigma \sqrt{2\pi})^3} \exp\left(-\frac{|\mathbf{x}|^2}{2\sigma^2}\right)

G(x)=(σ2π

)31exp(−2σ2∣x∣2) through separable mean filtering iterations, operating on voxel neighborhoods. This is particularly useful for noise reduction in SDFs, implemented via the LevelSetFilter class with optional masking. The Laplacian filter applies the discrete heat equation $\phi^{n+1} = \phi^n + \Delta t \cdot \nabla^2 \phi^n$ , where $\Delta t = \frac{dx^2}{6}$ (with $dx$ as voxel size) and $\nabla^2$ is the 6-neighbor stencil Laplacian, equivalent to mean curvature flow for narrow-band level sets and less costly than full curvature computations. Both filters track the zero isosurface during iterations to maintain SDF validity.^[25]^[24] Advection and morphing operations integrate velocity fields to evolve level sets, commonly applied in fluid simulations. The LevelSetAdvection class performs hyperbolic advection using total variation diminishing (TVD) Runge-Kutta schemes (orders 1–3), integrating the velocity field via user-provided functors that evaluate at arbitrary points and times, with CFL-conditioned time stepping for stability. For broader volume morphing in fluids, the VolumeAdvection tool employs semi-Lagrangian integration schemes (including basic semi-Lagrangian, midpoint, and higher-order variants like RK3/RK4 or BFECC), backward-tracing characteristics along velocity fields to advect scalar or vector densities while supporting narrow-band level sets. These methods ensure mass conservation and sparsity preservation during deformation.^[26]^[27] To maintain computational efficiency after these operations, OpenVDB includes topology optimization via pruning and voxelization. The prune method recursively removes inactive leaf nodes and tiles whose values match the background, in sparse regions without altering active topology. Voxelization, such as converting boolean or fog volume topologies to level sets via topologyToLevelSet, rasterizes active/inactive voxel interfaces into narrow-band SDFs using distance propagation, ensuring post-operation grids remain optimally sparse for subsequent computations.^[28]^[29]^[5]

File I/O and Serialization

OpenVDB employs a binary file format optimized for sparse volumetric data, featuring chunked storage that organizes data blocks hierarchically to minimize redundancy. Each file includes comprehensive grid metadata, such as the world-to-index-space transform, voxel size, and grid class (e.g., level set or fog volume), enabling accurate reconstruction of the volumetric structure upon loading. This format supports multiple grids within a single file, identified by unique names or ordinal indices like "" for the first unnamed grid, facilitating efficient handling of complex scenes with layered data.^[5] Reading and writing operations are managed through the io namespace, primarily via the io::File class, which acts as an archive for disk-based grid serialization. The readGrid function loads an entire grid or a partial subset defined by a world-space bounding box, while write functions serialize one or more grids to a file, optionally including statistical metadata like active voxel counts. These operations support instancing, where shared tree structures are written only once to avoid duplication across grids, and allow configuration of serialization options such as saving single-precision floats as half-precision for compactness. The format incorporates compression mechanisms like ZIP or Blosc to further optimize file sizes during I/O.^[30] For interoperability, OpenVDB files (.vdb) can be directly imported into compatible software, including McNeel's Rhino, which provides native support for loading and manipulating VDB volumes since version 8. Export capabilities include conversion to OpenEXR for 2D slices, where volumetric data is rendered as tiled image sequences suitable for compositing pipelines. Sequence formats, common in animation workflows, are handled by loading the initial file in a numbered series (e.g., frame_0001.vdb), with the library inferring the sequence for temporal data.^[31]^[32]^[5] Backward compatibility is maintained through versioned headers in the file format, which include a magic number, format version, and library version for validation. Upon opening a file, the io::File class checks the format version using functions like checkFormatVersion, throwing an error only for incompatible older versions while ensuring seamless loading of files created with prior library releases. Unique identifiers like UUIDs further aid in verifying file integrity across different environments.^[30]

Applications and Use Cases

Visual Effects and Film Industry

OpenVDB plays a pivotal role in visual effects (VFX) pipelines, enabling studios to manage complex sparse volumetric data for simulations and rendering of effects like smoke, fire, fluids, and destruction. Developed initially at DreamWorks Animation, it has become an industry standard adopted by major VFX houses, including Industrial Light & Magic (ILM), which contributed enhancements to solidify its use in production workflows.^[33] In film productions, OpenVDB has been employed for intricate effects sequences. For instance, ILM utilized OpenVDB in Transformers: Age of Extinction (2014) for simulating dust, explosions, and destruction effects in dynamic action scenes, such as Grimlock's interactions, leveraging its sparse structure for efficient handling of high-resolution volume data.^[34] At DreamWorks Animation, OpenVDB powered high-resolution animated clouds in Puss in Boots (2011), allowing for detailed atmospheric effects without the memory demands of traditional dense grids.^[11] More recently, Disney's VFX team relied on OpenVDB for simulating monstrous storms and ocean waves in the climactic sequences of Moana 2 (2024), facilitating seamless integration of large-scale fluid dynamics into the film's narrative.^[35] A key benefit of OpenVDB in VFX is its ability to process teravoxel-scale datasets for destruction and fluid simulations, preventing memory crashes that plague dense volume representations while maintaining high fidelity.^[2] This sparse hierarchical approach supports efficient storage and rapid access, crucial for iterating on massive effects like city-scale debris or turbulent water flows in blockbuster productions.^[11] As an open interchange format, OpenVDB facilitates smooth data flow across VFX pipeline stages—from simulation in tools like Houdini to rendering in engines such as RenderMan—ensuring compatibility and reducing bottlenecks in collaborative studio environments.^[2]

Scientific Computing and Simulations

OpenVDB's sparse hierarchical data structure enables efficient handling of large-scale volumetric datasets in scientific computing, where traditional dense grids often become computationally prohibitive for simulations involving complex, irregularly distributed phenomena. By storing only non-zero voxels and supporting dynamic topology changes, it facilitates numerical simulations that require high-resolution representations without excessive memory overhead, making it suitable for domains such as physics-based modeling and data analysis.^[8] In fluid dynamics, OpenVDB integrates with computational fluid dynamics (CFD) solvers to model turbulence and airflow in aerospace applications, allowing researchers to process billion-cell simulations efficiently. For instance, it has been used to visualize and analyze airflow around aircraft models, capturing wake vortices and turbulent structures by resampling unstructured CFD data into sparse volumes for scalable rendering and post-processing.^[36] This coupling supports turbulence modeling in research environments, where the library's tools for level sets and narrow-band operations aid in simulating incompressible flows and boundary interactions without full grid materialization. For medical imaging, OpenVDB represents computed tomography (CT) and magnetic resonance imaging (MRI) scans as sparse volumes, enabling analysis of anatomical structures by focusing computational resources on regions of interest, such as organs, while ignoring surrounding empty space. Neurological MRI data, for example, can be converted to VDB format to support 3D visualizations and simulations of brain tissue mechanics, with the structure's compression reducing storage needs for high-resolution datasets typically exceeding hundreds of gigabytes.^[37] This approach enhances workflows by providing fast access to voxel neighborhoods for computations in biomechanical modeling. In climate modeling, OpenVDB stores atmospheric data grids for global simulations, as demonstrated in analyses of aerosol distributions influenced by monsoons, where sparse representations handle vertically layered, time-varying volumes from satellite and reanalysis data. Organizations like NASA and NOAA benefit from its ability to manage irregular, high-altitude atmospheric fields without dense interpolation, supporting simulations of pollutant transport and weather patterns over oceanic regions. The library's unbounded index space accommodates planetary-scale grids, facilitating iterative solvers for geophysical equations.^[38]^[8] A key advantage of OpenVDB in these applications is its scalability to massive datasets, such as billion-voxel CFD outputs or terabyte-scale imaging volumes, achieved through hierarchical compression and on-demand access that avoids loading entire arrays into memory—potentially enabling exabyte-scale simulations by processing only active regions. This sparsity preserves computational efficiency in distributed environments, allowing simulations to run on standard hardware clusters while maintaining precision for scientific validation.^[36]^[5]

Integration in Software Tools

OpenVDB has been natively integrated into SideFX Houdini since version 13.0, released in 2013, allowing users to work with procedural volumes directly within the node's volume toolset for tasks such as simulation and rendering.^[39] This integration includes support for converting between OpenVDB grids and Houdini's native volume primitives, as well as VEX scripting and Mantra rendering capabilities for VDB volumes.^[40] The OpenVDB Houdini toolkit provides additional nodes for geometry-to-volume conversion and visualization, enhancing workflow efficiency in procedural modeling environments.^[41] In Blender, OpenVDB support is available through built-in volume objects introduced in version 2.81 (2019), enabling the import and rendering of OpenVDB files as volumetric data for simulations like smoke and fire.^[42] Python bindings facilitate add-ons that extend this functionality, such as custom importers for VDB sequences and shaders optimized for fluid rendering in Cycles and Eevee.^[43] These tools allow Blender users to integrate OpenVDB assets from external simulations without extensive preprocessing, supporting both static and animated volumes.^[44] Unreal Engine incorporates OpenVDB through plugins like the experimental unreal-vdb tool developed by Eidos-Montréal, which enables importing .vdb files and sequences for real-time visual effects in game development and virtual production.^[45] Updates in Unreal Engine 5.5 (2025) have improved VDB handling, including attribute tweaking, console variable enhancements for quality control, and integration with the Level Sequencer for animated playback.^[46] This allows for efficient loading of sparse volumes, reducing memory usage in dynamic scenes compared to traditional mesh-based approaches.^[47] At Pixar, OpenVDB is integrated into animation pipelines via Alembic for caching and interoperability, particularly in RenderMan workflows where VDB volumes are exchanged between tools for high-fidelity rendering of procedural effects.^[48] This custom setup leverages Alembic's time-sampled data storage to handle OpenVDB grids in USD-based scenes, ensuring seamless transfer across Pixar's production ecosystem without data loss.^[49] Such integrations support the studio's emphasis on scalable volumetric assets in feature films.^[50] OpenVDB has also seen emerging applications in real-time rendering and AI-accelerated simulations as of 2025, including integrations with NVIDIA Omniverse for collaborative VFX workflows and tools for machine learning-based volume processing.^[2]

Community and Ecosystem

Licensing and Open-Source Aspects

OpenVDB is distributed under the Apache License, Version 2.0, a permissive open-source license that permits commercial use, modification, and distribution while requiring attribution and preservation of copyright notices.^[8] This licensing model replaced the prior Mozilla Public License 2.0 with the release of OpenVDB 12.0 in November 2024, enhancing flexibility for integration into proprietary software without copyleft obligations.^[18] The Apache 2.0 terms explicitly grant patent rights and require contributors to notify of any known patent claims, fostering broader adoption in production environments.^[51] Governance of OpenVDB falls under the Academy Software Foundation (ASWF), established in 2018, with OpenVDB serving as its inaugural hosted project to ensure sustained development and industry collaboration.^[52] The OpenVDB Technical Steering Committee (TSC), chaired by Ken Museth of NVIDIA, directs technical decisions and comprises experts from key studios including Jeff Lait of SideFX and Dan Bailey of Industrial Light & Magic.^[2] This structure promotes coordinated evolution of the library while aligning with ASWF's mission to support open-source tools for visual effects and animation. Contributions to the project necessitate a signed Contributor License Agreement (CLA), which grants the ASWF and contributors perpetual rights to use submitted code under the project's license.^[53] Guidelines stress adherence to backward compatibility, particularly for the file format and application binary interface (ABI), with non-compatible changes limited to major version releases to minimize disruption for users.^[8] All pull requests must include comprehensive unit tests and pass continuous integration checks to uphold code quality and reliability.^[54] The project officially supports derivatives and extensions, such as OpenVDB AX, an integrated C++ library and domain-specific language for high-level volume and point data manipulation, including shading computations on GPUs.^[55] This modular approach allows specialized enhancements while maintaining core library stability.

Adoption and Contributions

The OpenVDB project has fostered a vibrant open-source community, with 89 contributors documented on Open Hub as of late 2025, reflecting sustained involvement from developers across industry and academia.^[56] Active engagement occurs through the project's GitHub repository, which maintains 168 open issues and 51 pull requests, alongside dedicated discussions on the Academy Software Foundation (ASWF) Slack in the #openvdb channel.^[54]^[57] Major adopters span leading visual effects studios, including Weta Digital, Industrial Light & Magic (ILM), and DreamWorks Animation, where OpenVDB supports high-resolution volumetric simulations in film production.^[58] Research institutions like NVIDIA have also leveraged the library for advancements in GPU-accelerated volume processing, such as the development of NanoVDB for real-time rendering.^[59] These adoptions underscore OpenVDB's role as an industry standard for sparse volumetric data handling. Contributions to OpenVDB have been notably enhanced by the Academy Software Foundation's participation in Google Summer of Code (GSoC) from 2020 to 2024, where the project served as a mentoring focus for student initiatives improving portability and performance.^[60]^[61] Metrics of adoption highlight OpenVDB's broad impact: the foundational paper introducing the VDB structure has accumulated 479 citations on Google Scholar, influencing research in computer graphics and scientific visualization.^[62] By 2025, the library is integrated into dozens of professional software tools, such as Houdini for procedural effects, Autodesk Maya for scene assembly, and LightWave for rendering workflows, enabling efficient volumetric operations in both commercial and open-source environments.^[39]^[41]^[63] The project's Apache 2.0 licensing has facilitated this collaborative growth by allowing seamless integration and modification across diverse applications.^[2]

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