Most of the materials used for manufacture, such as wooden boards, metal sheets, and paper, are planar and nearly inextensible. Bending this kind of material is a method to form objects that avoids waste and reduces gluing costs. However, the resulting shape is limited to developable surfaces. Due to this limitation, this method lacks flexibility in design. This problem can be addressed by adding slits to the material, allowing the conformation of a single sheet into expressive surfaces with high flexibility.

In this paper, we propose an interactive design system for this kind of geometry. The material used in this work is a rectangle containing parallel slits. The regions between slits are called strips, and by bending them, we can simulate the desired shape. Both flexibility and the geometric constraints were satisfied by a numerical optimization approach. The proposed system computes the better bending shape of strips considering smoothness of surface and user input. We show the effectiveness of our system with evaluation experiments.