Designers often create physical works-like prototypes early in the product development cycle to explore possible mechanical architectures for a design. Yet, creating functional prototypes requires time and expertise, which discourages rapid design iterations. Designers must carefully specify part and joint parameters to ensure that parts move and fit and together in the intended manner. We present an interactive system that streamlines the process by allowing users to annotate rough 3D models with high-level functional relationships (e.g., part A fits inside part B). Based on these relationships, our system optimizes the model geometry to produce a working design. We demonstrate the versatility of our system by using it to design a variety of works-like prototypes.

The deformable registration of a preoperative organ volume to an intraoperative laparoscopy image is required to achieve augmented reality in laparoscopy. This is an extremely challenging objective for the liver. This is because the preoperative volume is textureless, and the liver is deformed and only partially visible in the laparoscopy image. We solve this problem by modeling the preoperative volume as a Neo-Hookean elastic model, which we evolve under shading and contour cues. The contour cues combine the organ's silhouette and a few curvilinear anatomical landmarks. The problem is difficult because the shading cue is highly nonconvex and the contour cues give curve-level (and not pointlevel) correspondences. We propose a convergent alternating projections algorithm, which achieves a 4% registration error.

Quantitative results with in silico and phantom experiments and qualitative results with laparosurgery images for two patients show that our method outperforms the state-of-the-art in accuracy and registration time.