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How to convert Universal Scene Description (.usd,.usda, .usdc.usdz) to DirectX (.x)?

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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

DirectX

.x files are the native 3D file format of the legacy Microsoft DirectX v2/v3 API and 3D toolkit. They were generally associated with 3D gaming whereby low polygon meshes with skinning (deformation) and "animation sets/clips" were the required norm. At the time of its introduction in 1995 there really wasn't any other similar 3D file formats which supported these capabilities in one, well defined and easily accessible format. Direct3D shipped for the first time in the DirectX 2.0 SDK in June 1996

Historically, the DirectX technology was developed a company called Rendermorphics of the UK which Microsoft purchased in February 1995. As little known history, 3 companies in the UK developed advanced realtime rendering toolkits prior to 1995: Argonaut Software (BRender), Criterion Software (RenderWare) and Rendermorphics (Reality Lab). Microsoft was to license the Argonaut 3D toolkit but opted to purchase the entire Rendermorphics company instead, at the last moment. As these various toolkits often sold for $50k at that time, the other two competitors eventually went out of business once Microsoft started giving DirectX away for free.

Okino knows of the .x file format well as it was the first company to properly and fully implement a DirectX importer and exporter, including full support for skinning and animation at a time when no other software provided such conversion support.

The DirectX file format had a long life until some people inside and outside of Microsoft started to push the FBX file format instead.

Universal Scene Description import converter's overview

DirectX export converter's overview