3D RGB Image Format and Visualization?

[neverhood311]

In your thesis, section 6.2, you say:

In addition, the display of the resulting voxel field could well bear some research. Most visualization techniques work on a 3D space of scalar data; it would be useful if some techniques existed to display a 3D field of RGB data.

Do you know if there's been much progress in this area? I'm aware that there's an incredible amount of research on 3D volume visualization, but does it all apply to this application? (specifically, viewing 3D image volumes that were created from a 4D renderer).

Also, do you know of a voxel file format designed to store RGBA data like this?