BUGS:
 * non-square volumes (if re-adjusting the settings with g3.region)
   are not exported correctly.

 * if 100 rows/cols/depth are there, only 99 rows/cols/depth will
   be exported to Vis5D: problem of center cell and corner cell

 * with -m flag the "Probe" crashes in Vis5D

G3D library bug?
        G3d_getValueRegion (map, x, y, z, d1p, typeIntern);                  
     produces output with different orientation comparing to:
        G3d_getValue(map, x, y, z, d1p, typeIntern);