dont suppose one exists?

Not that I'm aware of. Why would you want one? I was always under the impression that the majority of PS effects and plugins work with either 8 bit, or more recently, some work with 16 bit int(not float). Plus I don't believe it even understands the notion of MIP mapped images. Those are all the things I think of when I think RAT.

Correct me if I'm wrong, though. I don't really keep on top of the photoshop world.

Cheers,

J.C.

i just thought it would be handy rather than converting textures with mplay.

If converting is what you are after you can try iconvert. Its a little command line tool to convert images to .rat (or other) file formats.