A method for generating a modified three-dimensional design last structure for footwear on a computer display, comprising: generating an initial three-dimensional last structure on the computer display; receiving user input data through a computer input system, the user input data indicating plural offset values for plural zones of the initial three-dimensional last structure, wherein the user input data indicates plural desired offset values in at least one region of an article of footwear selected from the group of: a toe region of the article of footwear, a heel region of the article of footwear, an ankle region of the article of footwear, a forefoot region of the article of footwear, and an instep region of the article of footwear, wherein the user input data indicating the offset values need not indicate a constant offset value over the plural zones; and using a computer processing system, generating a modified three-dimensional design last structure for the footwear on the computer display based on the initial three-dimensional last structure and the user input data indicating the plural desired offset values, wherein the modified three-dimensional design last structure as rendered on the computer display has an increased thickness as compared to the initial three-dimensional last structure, wherein the increased thickness is based on the user input data indicating the plural desired offset values, and wherein the modified three-dimensional design last structure is rendered on the computer display so as to simulate a desired thickness of an upper material placed on the initial three-dimensional design last structure so as to simulate an appearance of an actual footwear upper. generating an initial three-dimensional last structure on the computer display; receiving user input data through a computer input system, the user input data indicating plural offset values for plural zones of the initial three-dimensional last structure, wherein the user input data indicates plural desired offset values in at least one region of an article of footwear selected from the group of: a toe region of the article of footwear, a heel region of the article of footwear, an ankle region of the article of footwear, a forefoot region of the article of footwear, and an instep region of the article of footwear, wherein the user input data indicating the offset values need not indicate a constant offset value over the plural zones; and using a computer processing system, generating a modified three-dimensional design last structure for the footwear on the computer display based on the initial three-dimensional last structure and the user input data indicating the plural desired offset values, wherein the modified three-dimensional design last structure as rendered on the computer display has an increased thickness as compared to the initial three-dimensional last structure, wherein the increased thickness is based on the user input data indicating the plural desired offset values, and wherein the modified three-dimensional design last structure is rendered on the computer display so as to simulate a desired thickness of an upper material placed on the initial three-dimensional design last structure so as to simulate an appearance of an actual footwear upper.