How to convert Siemens NX
to U3D?

Siemens NX

A PRT file is a model part file saved in a three-dimensional model format used by Unigraphics, a 3D CAD program. It contains surface and solid information for a single part. PRT files are saved in a binary format, similar to an Alias wire model and an SDRC (Structural Dynamics Research Corporation) model.

U3D

Universal 3D (U3D) is a compressed file format standard for 3D computer graphics data.

The format was defined by a special consortium called 3D Industry Forum that brought together a diverse group of companies and organizations, including Intel, Boeing, HP, Adobe Systems, Bentley Systems, Right Hemisphere and others whose main focus had been the promotional development of 3D graphics for use in various industries, specifically at this time manufacturing as well as construction and industrial plant design. The format was later standardized by Ecma International in August 2005 as ECMA-363.

The goal is a universal standard for three-dimensional data of all kinds, to facilitate data exchange. The consortium promoted also the development of an open source library for facilitating the adoption of the format.