Thank you very much Paul, your code does work for me!
I have 3 more questions:
(1) What's the orientation code (LPI, RAI?) in your "sphere_coords.1D" file? I am trying to display my ROI balls against the background of MNI_N27 surface so coded my coordinates in LPI orientation, but they are far off the intended locations in the display.
(2) How does this "Nidos" way differ from the "isosurfaces" way on showing ROIs in suma? Why does the "isosurfaces" way not work in this case?
(3) What if one wants to show spheres and activation blobs (irregular shape in a volume dataset) together and against a background of surface? Now it seems to me that "suma -niml" with "Nidos" can work for spheres and "suma -vol" can work for blobs (but with the issue of color homogeneity). How would you approach it? Is there an example page for that?