Interactive design of castable shapes using two-piece rigid molds
Computers & Graphics 2019

Oded Stein        Alec Jacobson        Eitan Grinspun

Columbia University       University of Toronto

Mold design and fabrication of bunny gummy candy. The original mesh (far left) is manipulated with the design tool (left) to produce a shape that is castable (center) with a two-piece rigid mold (right). The resulting shape is then fabricated as candy (far right).


Two-piece rigid molds are particularly amenable to mass-manufacturing. Arbitrary objects cannot be realized with such a mold, because the cast will collide with the mold during removal. Most shapes are far away from being castable, i.e., realizable with such a two-piece rigid mold. When starting with an arbitrary shape, large deformations are needed to produce castable shapes. Such large deformations require user interaction together with a design process that is aware of fabrication constraints. We present such a design tool to generate two-piece rigid molds separated by a planar cut for a wide variety of shapes. Our casts can be produced in one single piece from a rigid, reusable mold and do not require further assembly after casting. We use a castability energy that can be optimized with gradient-based methods combined with an elastoplastic deformation based on the as-rigid-as-possible method. The tool enables a designer to deform an input shape significantly and arrive at an output shape that is castable.




title = "Interactive design of castable shapes using two-piece rigid molds",
journal = "Computers & Graphics",
volume = "80",
pages = "51 - 62",
year = "2019",
issn = "0097-8493",
doi = "",
author = "Oded Stein and Alec Jacobson and Eitan Grinspun"


We would like to thank Henrique Maia and Sandra Chiritescu for helping with the fabrication process, David Levin for interesting discussions on casting and molds, Sarah Kushner, John Kanji, and Chang Xiao for proofreading, as well as P. Herholz and P. Li for sharing their code with us. We also thank Chocoladefabriken Lindt & Spr√ľngli AG for allowing the use of their images and videos. This work was funded in part by NSERC Discovery Grants (RGPIN2017-05235), NSERC DAS (RGPAS-2017-50938), and the Canada Research Chairs Program. Eitan Grinspun was supported in part by a Fields Institute Fellowshop. This work is funded in part by the National Science Foundation Award NSF CCF-17-17268.