Hi, Trying to color a volume according to "volume data" I get the same numerical values for all colors and a speckled appearance. When using "volume data gradient norm" I get the expected colors, i.e. strong local changes of the volume data are red and spots where there is essentially no change are in blue. How is this possible? If I understand correctly, "volume data gradient norm" colors according to the first derivative of "volume data" or is this wrong? Do I need something like a normalization? Thanks a lot for explanations, best, Dieter ------------------------------------------------------------------------ Dieter Blaas, Max F. Perutz Laboratories Medical University of Vienna, Inst. Med. Biochem., Vienna Biocenter (VBC), Dr. Bohr Gasse 9/3, A-1030 Vienna, Austria, Tel: 0043 1 4277 61630, Fax: 0043 1 4277 9616, e-mail: dieter.blaas@meduniwien.ac.at ------------------------------------------------------------------------