One of Alberti's instructions, in his book on sculpture, was to measure the "most beautiful" parts of a person and then gather the measurements of lot of people (by gender) who were also deemed beautiful in the same places and then average those measurements. His idea was that many people are beautiful in some ways and not in others (such as beautiful face, but fat belly) . In his book he included long list of such measurements. His underlying idea was that the artist can instinctively notice what parts of a person are beautiful but will need to find many people to assemble one sculptural figure that is near perfect. The averaging, to him, was a way to discover what Nature's ideal was. He claimed that this was a method of the ancients (not so). What's interesting about this is the effort to objectify proportions for the figure, just as one could objectify proportions for architecture.
A lot of Ren. artists could care less about the religious subject matter they were hired to portray. What they competed with one another for was the best idealized portrayal of the figure in action, in space. wc
