This was investigated and postponed due to a very large changes required:

 Major design improvement :   Multiresolution Multilayer volmetric entities.
Since the beginning of FireVoxel, only volumes of the same voxel count and size are allowed to be combined in the Multilayerr volumetric entities.
New design relaxes this requirement, by demanding ONLY the physical dimensions of the layers to match so they can be combined into Multilayer volumetric entities.

Motivation: one of the important issues is the presentation of the Registration results. In 4D PET to MPRAGE registration, we desire to keep the dimensions of the MPRAGE intact.  But reformatting 220-timepoint PET volume to MPRAGE dimensions leads to multi-GByte volumes.  Solution is to keep registration results at the resolution close to original, while able to overlay it over the higher resolution target.

There are other applications of this.  If I am not mistaken, we were considering registering the prostate DCE exam to biopsy that have a much higher resolution.  It is a similar problem with the size of the registered source.

In short, we want to be able overlay registration result without the explosive and redundant data increase.

It is approached pragmatically, i.e. only currently used workflows would be modified and verified. We will adjust other multilayer functionality as we go.  The biggest task  and modification of the UI that I foresee is the Vector ROI issues, its dialog etc.