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Universal Scene Description Zipped (USDZ)

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Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

Full name Universal Scene Description Zipped (USDZ)
Description

Universal Scene Description Zipped (USDZ) package, developed by Pixar Animation Studios and described in the USDZ File Format Specification, version 1.2 (referenced below), is an uncompressed, unencrypted ZIP archive format created to address content delivery concerns. Using a USD plugin mechanism design, USDZ “contains and proxies for files of other formats embedded within the archive.” The files are referred to as packages and “the design rests on a new Ar-level abstraction of a package, of which the UsdUsdzFileFormat is the first implementation.”

According to Apple Newsroom, Apple Unveils ARKit 2, June 2018, Apple, collaborating with Pixar, introduced “a new open file format with iOS 12, USDZ, which is designed to more deeply integrate AR throughout iOS and make AR objects available across the ecosystem of Apple apps...like Messages, Safari, Mail, Files and News, while retaining powerful graphics and animation features. Using USDZ, Quick Look for AR also allows users to place 3D objects into the real world to see how something would work in a space.” As of Fall 2018, USDZ support was available on updates for iPhone 6s and later, all iPad Pro models, iPad 5th generation and iPad 6th generation.

USDZ Package:

The USDZ package absolute layout requirement is data for each file begin on a 64-byte alignment with the package.

A USDZ file is read-only, to edit the contents users must first unzip the package and edit the parts using appropriate tools.

Per specification, "a USDZ package can contain only file types whose data can be consumed by the USD runtime via mmap, pointer memory, or threadsafe access to a File *(i.e. solely pread-like access)." Curren file types include:

  • USD (first file in package must be a native usd file) – USDA, USDC, USD
  • Image – PNG, JPEG
  • Audio – M4A, MP3, WAV (specification preferred order)

Alembic (ABC) files are currently no allowed.

The USDZ Specification also describes details and rationales for the USDZ package, including USD constraints, packaging considerations, and toolset.

Uses of USDZ:

USDZ files are for 3D content delivery between applications in their 3D-creation pipeline, as well as displaying 3D and AR content on iOS 12+ devices.

Production phase

Can be used across all areas of production. Users can create and share USDZ packages, while developers can use them throughout their 3D-creation pipeline, although a USDZ file is read-only, to edit the USD parts the contents would need to be unpacked.

In 2018, Apple announced USDZ format for displaying AR content without the use of a third-party app with the release of iOS 12. According to Developer.Apple.com, "USDZ is available for iOS 14.0+, iPadOS 14.0+, macOS 11.0+, Mac Catalyst 14.0+, tvOS 14.0+, watchOS7.0. and Xcode 12.0+."

Relationship to other formats
    Subtype of ZIP_PK, ZIP File Format (PKWARE)
    Contains USD, Universal Scene Description
    May contain USDA, USD Human-Readable UTF-8 Text File. Not described separately on this website at this time.
    May contain USDC, USD Random-access "Crate" binary File. Not described separately on this website at this time.
    May contain PNG, Portable Network Graphics
    May contain JPEG, JPEG Image Encoding Family
    May contain M4A, MP4_FF_2, MPEG-4 File Format, Version 2
    May contain MP3, MP3 File Format
    May contain WAVE, WAVE Audio File Format

Local use Explanation of format description terms

LC experience or existing holdings The Library of Congress has a small number of USDZ files in its collections.
LC preference See the Recommended Formats Statement for the Library of Congress format preferences for Design and 3D formats.

Sustainability factors Explanation of format description terms

Disclosure

USDZ is a single object, uncompressed ZIP archive that is allowed to contain USD, USDA, and USDC files. USD is an open-source project released by Pixar Animation Studios. See USD for more information.

    Documentation

The official USD website, openusd.org, provides USDZ File Format Specification.

Apple, working with Pixar, developed a set of new schemas that extend the USDZ format for Augmented Reality (AR) cases, such as in AR Quick Look and RealityKit.

Adoption

The USDZ archive format was designed to utilize the USD format for 3D content delivery, designing the archive format to address content concerns. However, Apple has adopted the USDZ format for 3D content across AR-enabled iPhones, iPads, and other iOS 12+ devices. 3D asset AR abilities include anchoring 3D content at a specific location in the real world, reacting to real-world situations, and/or connecting audio effects to a location. Apple’s AR Quick Look previews AR and 3D content.

Currently, Android devices do not support the USDZ format. There are some third-party options for USDZ conversions, such as Adobe Project Aero (first Adobe Creative Cloud Suite company to announce support for USDZ), Adobe Substance Painters, Autodesk Maya, and Quixel.

According to Janko Roettgers in Apple is a Massive Force in AR. It’s Also Been Holding the Technology Back, May 2022, “WebXR makes it possible to run AT experiences in a browser, allowing people to launch immersive experiences directly from a website... Google’s Chrome browser for Android began supporting WebXR in beta in 2018; Samsung and Opera added support to their respective mobile browsers in 2020. Apple, on the other hand, has yet to add WebXR support to Safari on iOS. At the same time, there is no avenue for other browser-makers to bring WebXR to the iPhone, as Apple forces them to use Safari’s WebKit rendering engine to build iOS versions of their browsers. Under the hood, the iOS version of Chrome is using Safari code — which means that Chrome on iOS isn’t able to support WebXR. This arrangement means WebXR is effectively out of reach on the iPhone.”

Comments welcome.

    Licensing and patents

No known concerns for generation and use of the format.

See USD.

Transparency

USDZ files are read-only. Users can edit USDZ files by using the “unzip” command through Terminal on Mac or iOS development devices. Users can also change the file extension to .zip and extract its contents, which then users can edit the separated file with compatible tools. See USD format for more information.

See USD.

Self-documentation

See USD.

External dependencies

See USD.

Technical protection considerations

IANA Regulations state “USDZ files are zip archives and are subject to the security risks of that format. No exhaustive security audit has been performed on the specification. The format provides no privacy or integrity services. Users wishing to provide such services externally can do so using available security protocols such as SSL/TLS."

See USD.

According the USDZ Specification, "a USDZ package is a zero compression, unencrypted ZIP archive", with the following key consideration: For efficient direct consumption, a package already loaded into memory or as a single file on disk, can use the most direct API’s available in USD for accessing the data contained within the package. No extracting files to disk or allocating more heap storage. Allowing compression or encryption would violate preconditions that allow format to access data via direct memory access.

Comments welcome.


Quality and functionality factors Explanation of format description terms

Other
3D Model Geometry

USDZ archive is the USD file which contains model, animation, and material definitions, the remaining files are images and audios applied to the model.

See USD.

3D Model Appearance

See USD.

3D Model Scene

See USD.

3D Model Animation

See USD.


File type signifiers and format identifiers Explanation of format description terms

Tag Value Note
Filename extension usdz
See https://graphics.pixar.com/usd/release/spec_usdz.html#mime-type.
Internet Media Type model/vnd.usdz+zip
See https://openusd.org/release/spec_usdz.html#mime-type.
Pronom PUID See note.  No Pronom PUID as of May 2023.
Wikidata Title ID Q54809843
See https://www.wikidata.org/wiki/Q54809843.

Notes Explanation of format description terms

General  
History

June 2018, at the Worldwide Developers Conference (WWDC), Apple introduced a viewer for displaying and sharing high-quality 3D content using Pixar’s USDZ format. Leveraging Pixar’s Universal Scene Description standard, USDZ delivers AR and 3D content to Apple devices. Apple developed a set of new schemas in collaboration with Pixar to further extend USD for AR use cases. USDZ delivers AR and 3D content to Apple iOS 12 devices.


Format specifications Explanation of format description terms


Useful references

URLs


Last Updated: 05/18/2023