Figure 10.17
One way to construct a CAD model for a shoe last. The algebraic surfaces are constructed by skinning a set of skeleton curves that are held by one or more spine curves. The last bottom profile, the bottom section curves, and the last section curves have spatial relationships; the dots in the figure indicate coincidence of intersecting curves, and surfaces are constrained to pass through the curves. The surfaces patches making up the last body (respectively, last top, and last bottom) have G1 continuity along their shared boundaries.