Vray also uses .tx files for the built-in library, so I would assume all Choas assets are either already in tx or will be.
The reason they use this format is the benefit of mip-mapping and render speed. A few other benefits listed below, these 3 links you can read more (
Vray,
Open as Tiff ,
Mip-Mapping ) but this is the TLDR;
- they are intended to increase rendering speed
- reduce aliasing artifacts
- files require less memory
- high-resolution mipmap image is used for high-density samples, such as for objects close to the camera
- lower-resolution images are used as the object appears farther away
- improve image quality by reducing aliasing and Moiré patterns that occur at large viewing distances
You can also open .tx files as TIFF to edit in photoshop and save as something else, Its not recommend to overwrite the file as you lose all the mip-mapping and optimizations. You have to use the maketx batch script for the time being. Would be nice is there was a simpler way but thats about all I know on the topic.