Sustainability of Digital Formats: Planning for Library of Congress Collections

Jupiter Tessellation (JT), defined in the International Organization for Standardization (ISO) document ISO 14306 is “an industry focused, high-performance, lightweight, flexible file format for capturing and repurposing 3D product definition data for visualization to enable collaboration and validation throughout the extended enterprise. The ISO 14306 format is streamable and contains compression for compact and efficient representation.” As described on the JT Wikipedia page, originally developed by Engineering Animation, Inc., and Hewlett Packard, it was eventually acquired by Siemens AG in 2007. In 2009, ISO stated that the JT specification had been accepted for publication and was officially published as ISO 14306:2012 in 2012, based on the Siemens JT specification version 9.5. The Second Edition of the specification was accepted in 2016 and published as ISO 14306:2017 in 2017 is the current version. See History.

As stated, ISO 14306:2017 cancels and replaces the first edition with the main changes compared to previous edition are as follows:

• Addition of a STEP B-Rep Segment based on the ISO 10303 STEP suite of standards;
• addition of a new geometry chapter listing all geometry segments in the annexes;
• updates of the documentation from the ProSTEP iViP industrialization guidelines;
• addition of a conformance clause;
• addition of a mapping table JT ISO to STEP;
• deprecation of the JT Brep segment;
• deprecation of the Product & Manufacturing Information (PMI) data segment which is superseded by the meta data segment.

ISO 14306:2017 specification is available for purchase (CHF 208), format information collected from Siemens JT File Format Reference Version 10.5 Rev-A 2019. See Notes.

According to Siemens, the JT format at its core it a scene graph with CAD specific node and attribute support. Triangles, lights, textures, materials, PMI, Precise Part definitions (B-Rep), metadata, and representation configurations are supported by the format.

Highlights of JT:

• Built-in support for assemblies, sub-assemblies and part constructs
• Flexible partitioning scheme, supporting single or multiple files
• B-Rep, including integrated support for industry standard Parasolid® (XT) format
• PMI in support of paperless manufacturing initiatives
• Precise and imprecise wireframe
• Discrete purpose-built Levels of Detail
• Triangle sets, Polygon sets, Point sets, Line sets and Implicit Primitive sets (cylinder, cone, sphere, etc…)
• Full array of visual attributes: Materials, Textures, Lights
• Hierarchical Bounding Box and Bounding Spheres
• Advanced data compression that allows producers of JT files to fine tune the tradeoff between compression ratio and fidelity of the data

Structure of JT:

JT files are structured as a sequence of blocks/segments.

• File Header Block: always first and contains information about the JT version, Table of Contents (TOC) location, and Loaders used to determine how to read the file, including GUID for the Logical Scene Graph Data Segment.
• TOC Segment: always required, contains information identifying and locating Data Segments. Contains one TOC Entry per individual Data Segment, with the essential function of the TOC Entry being to map a Segment ID to an absolute byte offset with the file.
• Data Segment: defines all the stored data, are “typed” based on general classification (Segment Types) of the data, and all have the same basic structure. Interpretation of the Data section depends on the Segment Type.
  • Logical Scene Graph (LSG) Segment: collection of objects (elements), graphical description of the model containing shapes and attributes representing the model’s physical components, properties identifying metadata, and hierarchical structure. Includes: Graph Elements, Node Elements, Attribute Elements, Property Atom Elements, and Property Table.
  • Meta Data Segment: stores large collections of meta-data in separate addressable segments.
  • Shape Leve of Detail (LOD) Segment: element that defines geometric shape definition data (vertices, polygons, normals, etc.) for a particular shape LOD.
  • Info Segment: text strings with authoring information, such as information on the system(s) used, provenance (origin), not information pertaining to, modifying, or supplementing the content.
  • Geometry Segments: elements that define a range of geometry definitions.
• Data: common structure of a list or multiple lists of Elements, consisting of header information describing type of object contained (Object ID).
• Object Data: interpretation depends on Object ID stored.

Uses of JT

As stated on Siemens’ website, JT is “widely used for communication, visualization, digital mockup and a variety of other purposes at a majority of the world’s leading manufacturing companies. JT has been accepted by ISO as an International Standard for 3D visualization. ...many JT Adopters use JT as a process format for workflows such as data exchange, supplier collaboration, and long-term data retention.”

In 2003, Siemens formed the JT Open Program, a global alliance of corporations and software suppliers that have built a community with the principle of promoting the use and adoption of 3D JT data. The program has over 100 members, including fortune 500 companies from around the world. Achievements by the JT Open Program include the publication of the JT format specification and the creation of the JT viewer, JT2Go.

According to CAD Exchanger supported formats, “JT files are used in product lifecycle management (PLM) software programs and their respective CAD solutions, by engineers and other professionals that need to analyze the geometry of complex products.”

An open standard, ISO 14306 is published by International Organization for Standardization (ISO).

ISO 14306:2017 Industrial automation systems and integration — JT file format specification for 3D visualization is available for purchase.

Siemens JT File Format Reference Version 10.5 Rev-A PDF is freely available to view online.

The JT format is widely used for 3D data visualization and communication through many major CAD systems, including AutoCAD LT, Creo CAD, Siemens NX, and Siemens Solid Edge.

JT is also a common language of Siemens PLM Components, 3D software development toolkits, and provides tools such as JT Open Toolkit/JT Utilities, JT Unity Plug-in, and the PLM XML SDK.

The JT Open Program and its members continue to work to expand the use of JT throughout industries. Some well-known members include Microsoft, LEGO, General Motors, Proctor & Gamble, Adobe, and Google LLC – X Development. See link for full list.

Siemens PLM Software Inc. (SPLM) – JT Data Format Reference Patent Clarification Notice.

SPLM owns one or more patents documented in JT File Format Specification and ISO 14306, but promoting the use of JT data for information interchange the patents are licensed on a royalty-free, non-exclusive basis for the term of each patent and for the purpose of developing software that produces and interprets JT data files that are compliant with the specification.

U.S. Patent Number: USA 20110199382, 8019788 and its corresponding patents in foreign jurisdictions.

JT is binary so it requires translation for human readability.

The JT format supports metadata with no limits to what metadata can be attached to nodes in the LSG, including PMI, user specific, creation information, etc.

JT stores metadata in separate addressable “late-loaded” segments (allows a JT file loader/reader to ignore a node’s metadata on initial load and instead late-load the metadata upon demand so file memory is no used till needed).

None beyond availability of supporting software. JT files are derived from CAD systems and used by visualization software tools that do not need the full capability of a CAD system.

None. Comments welcome.

The JT format supports mesh (triangulated facets) and B-Rep geometry. Meshes are a big focal point of the format and lots of things are built around them. Part-assembly hierarchy provides a mechanism to store multiple meshes for a part, representing different levels of detail (LODs).

B-Rep defines a 3D body via set of geometrical entities (points, curves, and surfaces) and topological entities (vertices, edges, faces, shell, solid). Geometrical provide definitions of body boundaries and topological trims the geometry and stores connectivity information.

JT files describe the 3D model appearance using Attribute Elements placed in the LSG as objects associated with nodes.

• Material Attribute Element defines properties such as ambient color, shininess, and bumpiness.
• Texture Image Attribute Element defines texture and mapping environment such as pixel format, data type, and size.

All other Attributes Elements define single default fields.

JT files describe the 3D model scene using LSG and Attribute Elements placed in the LSG as objects associated with nodes.

• The LSG describes the model and contains graphic shapes and attributes representing the physical components of the scene.
• Draw Style Attribute Element defines various aspects of the graphics state/style used for rendering geometry, such as back-face culling, lighting, and shading.
• Light Set Attribute Element defines a list of lights, stores the number of lights and the referenced Light Object ID. Light source can be defined by direction, position, or angle.

No support for animation. See Notes.

Comments welcome.

ISO JT 3rd Edition

According to Prostep IVIP PSI 14-2 JT Recommendation, June 2021, “Starting in 2019, an effort has been made to publish a third version of the ISO standard. The original intention was to incorporate the suggestions for additional and more detailed information... to cover the latest JT version 10.5 in this third version and publish it. It is, however, at present no possible to say if and when an ISO JT V3 will be published.”

Note on Animation

Siemens JT Open Community Forum thread stated, “JT files are able to store results from analysis, including representations of deformation, but they do not store animation or motion. JT files can represent motion when used with additional data, stored in a .vfm file, that describes a series of transforms using the data in the JT file. VFM motion files can be generated with Teamcenter Visualization products"

The JT format was originally developed by Engineering Animation, Inc. and Hewlett Packard as the Direct-Model toolkit (initially Jupiter). When EAI was purchased by UGS, JT became a part of UGS Corp.’s suite of products Siemens PLM Software (formerly UGS Corp.) use it for product visualization, collaboration, and CAD data exchange.

On 2009 September 18, JT specification was accepted for publication as an ISO Publicly Available Specification (PAS14306). In December 2012, it was published as ISO 14306:2012 Industrial automation systems and integration -- JT file format specification for 3D visualization.

In parallel of the publication of ISO 14306:2012, ISO has launched a follow-up project to better integrate JT in the ISO standards framework by introducing the STEP B-Rep Geometry definition as the normative geometry for JT in ISO 14306 ed2. In November 2017, ISO 14306:2017 was published.