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Section: New Results

Modeling for Fabrication

We pursued our research regarding automatic modeling techniques for fabrication, where an algorithm takes into account fabrication constraints to simplify the modeling process. This year we have worked on three projects in this area: the modeling of mechanisms from incomplete 2D definitions, the modeling of self-supporting tight enclosures to assist the fabrication process, and the interactive sculpting of support-free objects.

3D Fabrication of 2D Mechanisms

Participants : Jean Hergel, Sylvain Lefebvre.

This project considered the automatic modeling of 3D mechanisms from an under-specified 2D model of the mechanism. Our approach casts the synthesis problem as an edge orientation problem in a graph, where graph nodes represent parts of the mechanisms and edges capture their interactions as analyzed by the 2D simulation of the mechanism. The edge orientation determines which parts include which others. Once all inclusions have been determined, we formulate a CSP to solve for the layering problem: each part is assigned a depth 'layer' in 3D. We finally compute the final geometry through CSG (boolean combinations of shapes). This work has been published in Computer Graphics Forum (proceedings of Eurographics 2015) [8] . It received an honorable mention from the best paper committee.

Self-supporting Tight Enclosures

Participants : Samuel Hornus, Sylvain Lefebvre, Frédéric Claux, Jérémie Dumas.

The aim of this project was to develop a technique to automatically generated a tight enclosure in the free space around an object. The challenge was to ensure that the enclosure stays close to the object and be as thin as possible while still being printable without collapsing. Such an enclosure finds at least two important applications : 1. as a protective skin to avoid artifacts when 3D-printing a multi-material object. 2. for generating as-large-as-possible cavities inside the printed object in order to minimized material usage and print time. The work is available as an Inria technical report [22] .

Interactive Sculpting of Support-free Objects

Participants : Tim-Christopher Reiner, Sylvain Lefebvre.

Tim Reiner, former PhD student at the Karlsruhe Institute of Technology, joined the team on a Post-Doc position to explore new ideas in the context of modeling, rendering, and fabrication. Starting in March 2015, he developed a voxel-based environment for interactive modeling. In a research project together with Sylvain Lefebvre, our team has derived novel techniques for sculpting support-free 3D shapes. These shapes have the property that they do not require support structures during fabrication on fused deposition modeling or resin-based printers. This work is currently under review.