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How to convert VRML (VRML2, VRML97, X3D) to Universal Scene Description (.usd,.usda, .usdc.usdz)?

PolyTrans|CAD+DCC performs mathematically precise CAD, DCC/Animation, GIS and BIM 3D file conversions into all key downstream 3D packages and file formats. Okino software is used and trusted throughout the world by many tens of thousands of 3D professionals in mission & production critical environments, backed by respectable personal support directly from our core development team.



VRML2 ("Virtual Reality Markup Language") is one of the very best of non-MCAD file formats, little appreciated and lost (mainly) to the annals of time. Many people (wrongly) believe that FBX is the primary "translation file format" but VRML2 pre-dated it by at least 10+ years and has equally good or better functionality (and in an open, non-proprietary specification). It was supplemented or augmented by the X3D (XML-based) file format in the mid 2000s. The Web3D Consortium supports the evolution of VRML2/X3D and of its acceptance as ISO and IEC standards.

Without getting into specifics, VRML2 can be considered a "rich file format" in terms of its functionality and capabilities, yet few software programs fully utilize all of that functionality. It could have, and should have, become the defacto "universal 3D file format" for data translation and long term storage but it did not have the clout nor marketing dollars that other newer formats had such as from Autodesk (FBX, DWF), Sony (COLLADA), Adobe+Intel (U3D), Dassault Systemes (3DXML) and others.

VRML1 and VRML2 are 3D file formats with a long and complex history. They were originally developed in the mid 1990s to define 'interactive 3D worlds' on the then-new World Wide WEB. However, statistically speaking, VRML2 became more well known as a high quality "data translaton and storage" file format, partly due to Okino pushing it as such a standard in the industry. It was implemented by a good number of 3D software packages and hence became a "reliable back door" to convert 3D assets out of those packages before FBX, DWF, COLLADA, U3D and other similar file formats came along in the mid to late 2000s, or glTF in the late 2010's.

It is also known as VRML2, X3D, Classic VRML, VRML97, VRML1 and Inventor2.


Universal Scene Description

The USD format (“Universal Scene Description”) is an open 3D model and scene format designed for efficient storage and streaming of 3D asset data. It is a high-performance extensible framework and ecosystem for describing, composing, simulating, and collaboratively navigating and constructing 3D scenes. An extensive overview of USD is provided in the Okino USD documentation.

Pixar Animation Studios originally created the USD platform (as its fourth generation variation after its Marionette & Preso systems) to improve studio-wide collaborative workflows. USD provides a concept of "scene composition", building a unified scene from potentially thousands of loosely-coupled source assets. For example, the mesh, rigging, materials, and animation for a single model might all come from different "layers" (files), each created and maintained by a different artist or department. Layers can store multiple "variants" of any given data, helping to solve problems of versioning/approval. The coupling between layers is very dynamic and loose, allowing for greater flexibility during the production process. The entire USD system is designed to facilitate a large studio making feature films, with all of the scale that that implies.

USD should be considered more of a code framework (“OpenUSD”) for use in group collaboration, to help with the aggregation of various 3D data sources into a unified scene through a process referred to as scene composition. A subset of that code framework provides for reading and writing USD disk-based files as well as rendering USD scenes (Hydra). The system is rather complex to implement (for software developers) and to use (from first principles) as a 3D graphics artist. The USD file format itself is not for faint of heart and is best read/written using the OpenUSD SDK + various programming APIs. More commonly used ASCII 3D file formats such as COLLADA, VRML2 and Wavefront OBJ are much easier to manipulate/understand/use on a human level basis.

File extensions used by the standard include:

  • .usd, Either ASCII or binary-encoded
  • .usda, ASCII encoded
  • .usdc, Binary encoded
  • .usdz, Zero-compression, unencrypted zip file