Hi TU,
Mantra (Houdini), Arnold, Clarisse are capable to render volumetric clouds/fx, with gi, scattering and all the whistles.
The result quality is good enough for my taste, for localized formation. But tools for creating those volumetric assets are not as easy to use than Terragen ... or at least I'm not really familiarized with them.
I also do thing those render engines are more versatile than Terragen, especially when lighting precision is important (small scale scene / hdr studio lighting), or when advanced raytracing effect are needed (sss, refraction, multiple gi bounces, hair rendering, etc).
And there is no disrespect from me, I appreciate Terragen for what it can do.
Anyway there is no reason we can't get both right (import/export) ?
Some 3d package are (badly ?) starting to play in Terragen/Vue field. And imho it's very important that Terragen start
to play better with others. Especially since format like .abc, or .vdb are in the game, helping to exchange all kind of data.