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Khronos Prepares glTF 2.0 to be Submitted for Transposition to an International Standard

by gltf

Interoperability specifications, such as Khronos open standards, can significantly widen their market recognition and adoption by becoming International Standards. International Standards are recognized throughout the world, and in many countries form the regulatory basis for public procurement of IT goods and services. An International Standard also provides important assurances of stability and longevity.

Working with ISO/IEC JTC 1

ISO/IEC JTC 1 is the premier body for International Standards in Information Technology (IT). JTC stands for “Joint Technical Committee,” and JTC 1 was created by a collaboration between ISO (the International Organization for Standardization) and the IEC (International Electrotechnical Commission). ISO is an independent, non-governmental international organization with a membership of over 150 national standards bodies, and the IEC (International Electrotechnical Commission) is the world’s leading organization for International Standards for electrical, electronic, and related technologies. JTC 1 standards are among the most universally recognized and accepted throughout the world.

JTC 1 has a Publicly Available Specification (PAS) transposition process that enables widely adopted specifications from Standards Developing Organizations (SDOs) in the industry to be recognized as International Standards. An SDO wishing to propose an International Standard must first be approved as a PAS Submitter after review of an extensive set of organizational criteria. Once approved, a PAS Submitter may put forward one or more of its specifications to JTC 1 for approval by its participating national standardization bodies and thereby international recognition. Currently, there are fourteen SDOs approved as JTC 1 PAS Submitters, including Khronos as the most recent addition.

glTF – The Journey to Becoming an International Standard

Khronos was approved as a ISO/IEC JTC 1 PAS Submitter In May 2021. The first specification that Khronos will submit for transposition to an International Standard is glTF 2.0. As a step in this process, Khronos has today released a new canonical glTF 2.0.0 specification. If the transposition ballot at JTC 1 succeeds, glTF 2.0.0 will become a JTC 1 International Standard sometime in 2022.

The new specification does not introduce technical changes that will directly impact existing tools and engines, but it does align glTF with the rigorous document quality criteria needed to be accepted as an International Standard:

  1. Consistent use of normative language according to IETF BCP 14
  2. Fully identifying and listing all external references
  3. Eliminating the assumption of OpenGL knowledge by expanding the Sampler and the Mesh Primitive sections, making the specification self-contained and more suitable for implementers without an OpenGL background

The JTC 1 PAS Submission process is designed to avoid slowing the momentum of successful industry standards. Khronos retains full control over the development and evolution of glTF, and if approved as an International Standard, glTF will remain royalty-free. glTF will continue to evolve and meet industry needs through Khronos glTF extensions and the incorporation of widely adopted extensions into Khronos glTF core specifications. In parallel, Khronos will make future PAS submissions to bring proven glTF functionality into updated versions of the International Standard when ready, and ensure that there is no divergence between glTF JTC 1 International Standards and the corresponding Khronos specifications.

glTF Technical Clarifications and Bug Fixes

While preparing the new version of the glTF specification, Khronos has taken the opportunity to incorporate technical clarifications:

  1. Added physical units for emission
  2. Clarified that certain JPEG and PNG features are not supported
  3. Conducted a full rewrite of the JSON encoding section, relaxing some of previously unenforced restrictions
  4. Clarified image media types detection
  5. Explicitly allowed Internationalized Resource Identifiers (IRI)
  6. Clarified suggested rendering of point and line primitives
  7. Clarified morph target accessor formats

Some minor bugs have also been rectified:

  1. Explicitly disallowed interleaved data for buffer views that do not contain vertex attributes
  2. Restored the vertex color definition from an earlier specification version
  3. Discouraged use of zero-length BIN chunks in GLB

Finally, the glTF specification tooling pipeline has been upgraded to align with Vulkan and other Khronos standards. glTF 2.0.0 is authored in the AsciiDoc markup language enabling high quality PDF and HTML versions of the final published specification. And just like Vulkan, Khronos is making the specification AsciiDoc source available under CC-BY 4.0 on GitHub for easier community feedback, contributions, and downstream remixing.

A Foundation for Forward Progress

The glTF specification is now cleaner, clearer, and more precise, creating a strong foundation for glTF’s continued evolution—both as a Khronos specification AND a future International Standard!

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