Figure 19. a plush toy and a balloon designed in our system.

Figure 22. Knitty system allows the user to design an original knitted toy by simply drawing the desired silhouette.

they enjoyed the process. These toys were their own creations and one-of-a-kind designs. Participants also gave us valuable feedback for future improvement. They wanted to have some auxiliary functions such as the ability to design symmetric parts and remove existing parts, but no one complained about the quality of the visual simulation. A perfectly accurate simulation is not necessary because many small variations inevitably occur during the real sewing and stuffing process.

Figure 20. Example of texture changed. these models have many thin parts.

Figure 21. Example of original plush toys designed and created by children in the workshop.

children, approximately 10–14 years old, joined the workshop accompanied by their parents. We gave a brief tutorial at the beginning and had them design their own plush toys using the system. It took about an hour for the design. They then printed the designed pattern and sewed a real toy in 3 h. Figure 21 shows a couple of plush toys created in the workshop. Participants quickly learned how to use the system and successfully designed the 3D models they wanted, with some help from volunteers. Furthermore,

7. ConCLuSion

We introduced a plush-toy design system as an example of our efforts to make CAD and CAE accessible to end users. The system allows the user to design a plush toy quickly and simply by combining simple sketching operations. The user draws the desired silhouette on the canvas, and the system automatically generates a 3D plush-toy model and a 2D cloth pattern. The system runs a simple physical simulation in the background so that the resulting 3D model is always a good estimate of the final sewn result. The user can construct a real plush toy by printing the pattern and sewing the resulting pieces together.

To demonstrate the effectiveness of the approach even further, we also developed a system for the design of knitted toys. 13 A knitted toy is a toy made of knitted yarn instead of cloth patches. One can construct a knitted toy by knitting according to a specific knitting pattern, but it is difficult to produce an appropriate knitting pattern for a desired 3D shape. The Knitty system allows the user to design an original knitted toy by simply drawing the desired silhouette (Figure 22). The system then generates a 3D knitted animal model and corresponding knitting diagram. We ran a workshop using this system and observed that children could use it to design their own knitted animals.

Interactive 3D modeling assisted by concurrent physical simulation can be a powerful tool in many other application domains. For example, if one could run an aerodynamic simulation during the interactive design of a paper airplane model, the entire geometry could be adjusted in an intelligent manner in response to the user’s simple deformation operations to produce a model that could actually fly. This kind of interaction would make it easier for designers to pursue aesthetic goals while satisfying engineering constraints. Real-time simulation does require high-performance computing resources, but some meaningful support should be possible by carefully limiting the target task and designing appropriate interfaces as shown in this paper. We hope that our work inspires more work in this direction.