Hi,
as far as I know there is only the possibility to have an input for a
2D array to matlab scriptnode. Thus you should convert your 3D data to
2D in LV and reconvert it in your matlab code into 3D.
When you select 3D data as an output of a script node it automatically
appears as 2D (but no data will be lost). So when you have to use it in
LV again as 3D data, what you have to do is reconvert it back from 2D
to 3D.
Hope this helps!