ParaView 6.0 and VTK 9.5: Better Together

We are pleased to announce the official releases of ParaView 6.0 and the Visualization Toolkit (VTK) 9.5. This occasion marks a strategic evolution in our release methodology, as we are synchronizing the release schedules of ParaView and VTK for the first time. This alignment is designed to deliver significant advantages to our user and developer communities.

The coordination of these releases is the result of considerable planning and effort by the respective development teams, aimed at fostering a more stable, predictable, and powerful ecosystem for scientific visualization.

The Strategic Rationale for Synchronized Releases

Aligning the release cycles of ParaView and its foundational library, VTK, is a procedural change with substantial impact. There are several benefits of this new strategy.

1. Streamlined Defect Resolution and Backporting

A principal advantage of synchronized ParaView and VTK releases is the simplification of the software maintenance process. When a defect is identified, particularly one that affects both the core functionality of VTK and its usage in ParaView, the remediation can be developed, tested, and integrated into a VTK minor version’s maintenance branch.  When the next patch version of VTK is released, a subsequent ParaView patch release can be based on it rather than a ParaView-specific branch of VTK. The elimination of this ParaView-specific branch streamlines the development process for defect resolution.

This process ensures that critical bug fixes can be backported more efficiently to the latest stable releases of both toolkits. Consequently, developers will no longer need to be concerned about compatibility between a VTK patch release and their ParaView version. Any patch to VTK 9.5.x will be engineered and validated to be fully compatible with ParaView 6.0.x.

2. Enhanced Dependency Stability and Flexibility

Historically, specific versions of ParaView were often tightly coupled to a narrow range of VTK git commits. This created a rigid dependency, which could present challenges for developers, package maintainers, and system administrators building ParaView from source or integrating it into larger software ecosystems.

The new synchronized release model addresses this issue directly. ParaView 6.0 is designed to build against any patch release within the VTK 9.5 series. Combined with the recently added ability to build ParaView against an external VTK, this provides a significant increase in flexibility, allowing site and package maintainers to update to the latest VTK 9.5 patch to benefit from recent bug fixes and performance enhancements with the confidence that it will not disrupt their ParaView 6.0 installation. This level of stability is invaluable for long-term projects and production environments.

3. Facilitating a True Pip-Installable Distribution

A primary motivation for this change is to evolve how ParaView is distributed via the Python Package Index (PyPI). Currently, the paraview package on PyPI bundles its own version of VTK to guarantee functionality, as it has historically required a very specific VTK version. This means that even if you have VTK installed, pip install paraview will install its own, potentially redundant copy.

The synchronized release schedule is the key to fixing this. By ensuring ParaView 6.0 has a stable and flexible dependency on the VTK 9.5 series, we can transition from bundling VTK to declaring it as a formal dependency.

In the near future, the paraview package will specify its VTK requirement (e.g., vtk>=9.5,<9.6). The installation process will then become much more intelligent:

# The future of ParaView installation
pip install paraview

When this command is run, pip will check if a compatible version of the vtk package is already installed. If it is, pip will use it. If not, it will download the correct version from PyPI as a separate dependency. This eliminates redundant libraries and represents a more robust, standard Python packaging approach, greatly simplifying deployment for all users.

4. Fostering a More Cohesive Development Ecosystem

Beyond the immediate technical advantages, aligning the release schedules promotes a more cohesive and collaborative development environment. The ParaView and VTK teams can better coordinate on feature development, API modifications, and long-term strategic roadmaps. This synergy is expected to yield more innovative features and a more powerful, integrated platform for advanced visualization.

Future Outlook

The concurrent release of ParaView 6.0 and VTK 9.5 represents more than a standard software update; it is a clear statement of our commitment to stability, usability, and the open source community. We believe this new synchronized release strategy will provide a stronger foundation for the future of scientific visualization.

We are optimistic about the possibilities this new paradigm enables and welcome community feedback. We encourage you to download the latest releases to experience the benefits of this new, streamlined era for ParaView and VTK.