The file extension MTX is used for 3D scene data in the so-called MetaStream format. It is an open streaming format that displays 3D content on web pages. An MTX file contains a so-called high-level description of a model with attributes and animations, while the textures and model geometry are stored in mts files.
To view the 3D data with a browser, the Viewpoint Media Player Plugin is required. The development has been discontinued for a long time, so that Mozilla Firefox 3.0 is no longer supported. In addition to the Internet Explorer, Safari on Apple Mac OSX can also be used.
In addition to some CAD programs (some only with a plugin), the long-running authoring program Adobe Atmosphere can handle the MetaStream format.
The Metastream 3 (MTS3) format is also referred to as the VET (Viewpoint Experience Technology) format.