Bend-It: Design and Fabrication of Kinetic Wire Characters

Abstract

Elastically deforming wire structures are lightweight, durable, and can be bent within minutes using CNC bending machines. We present a computational technique for the design of kinetic wire characters, tailored for fabrication on consumer-grade hardware. Our technique takes as input a network of curves or a skeletal animation, then estimates a cable-driven, compliant wire structure which matches user-selected targets or keyframes as closely as possible. To enable large localized deformations, we shape wire into functional spring-like entities at a discrete set of locations. We first detect regions where changes to local stiffness properties are needed, then insert bendable entities of varying shape and size. To avoid a discrete optimization, we first optimize stiffness properties of generic, non-fabricable entities which capture well the behavior of our bendable designs. To co-optimize stiffness properties and cable forces, we formulate an equilibrium-constrained minimization problem, safeguarding against inelastic deformations. We demonstrate our method on six fabricated examples, showcasing rich behavior including large deformations and complex, spatial motion.

Publication
ACM Transactions on Graphics (SIGGRAPH Asia)

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