How to Introduce Shape Characteristics to Last Design
We developed a method of last design in order to introduce information on human foot morphology by using the FFD (Free Form Deformation) technique. FFD control lattice points are defined around an object, and the object is deformed by moving the control points.
In the figure, control points are defined around a "standard" foot, and the control points are automatically moved so that the "standard" foot deforms into a flat foot. Here the movement of the lattice points are considered as a transformation function from a "standard" foot to a flat foot. When a last is placed in the transformation function, a new last that would fit a flat foot may be obtained.
This is an example. The movements of lattice points that transform a "standard" foot (blue figure) into a flat foot (red figure) were calculated. The pattern of the lattice movement represents the difference between the two feet. In top view, the resultant lattice points arranged in a "S" pattern represent the bentness of foot axis. In the side view, the lattice points moved downward at the tarsal part to represent the low arch.
An existing last was placed in the deformed lattice. The resulting last reflects the morphology of the foot. Though foot morphology is a very important aspect, the function of the last and the shoe should be also taken into consideration.