Bill Mack is the world’s preeminent relief sculptor The relief form – in Mack’s case, primarily “alto relief” – originated in ancient temple friezes and marble sepulchers and is virtually nonexistent in galleries anywhere . To excel in this exacting form, in which foreshortening poses daunting technical challenges, Mack is also a master draftsman. Each relief derives from painstaking studies of the foreshortened figure-a classic skill that is a major factor in to the quality of his reliefs.