Section: New Results

By-example Synthesis of Structurally Sound Shapes

Participants : Jonas Martínez Bayona, Jérémie Dumas, Sylvain Lefebvre.

This is a collaboration with Li-Yi Wei (HKU) on a first project, An Lu (Inria/TU. Munich), Jun Wu (TU. Munich) and Christian Dick (TU. Munich) on a second project.

This work is at the heart of the ERC ShapeForge and considers the by-example synthesis of shapes under structural constraints. We considered two views of the problem that lead to different methodologies.

In a first approach, our goal is to cover a surface with a pattern – an operation akin to texturing in Computer Graphics. The pattern is however used to define the final shape, by determining which parts of the surface are solid or empty. The method operates on a thin voxel shell and does not require any parametrization of the input surface. The pattern is synthesized using a novel formulation for by-example pattern synthesis along surfaces. It is analyzed for structural weaknesses and this information is fed back to the pattern synthesizer, so that seamless reinforcements are added to the structure. We collaborated with researchers from T.U. Munich to analyze the structural behaviour of our structures, and developed a fast evaluation scheme that can be used within our optimization loop to guarantee structural soundness of the resulting design. The work was published in ACM Transactions on Graphics in 2015 [9] (proceedings of SIGGRAPH 2015).

In a second approach we considered the synthesis of shapes that are as rigid as possible under specific boundary conditions and using a prescribed amount of material, while resembling a given input example pattern, as illustrated in Figure 3 . Our method is inspired by the field of topology optimization, where rigid shapes are optimized but without any appearance constraints. Our algorithm generates shapes that resemble the input exemplar while being within a user specified percentage of the most rigid shape obtained without the appearance objective. The work was published in ACM Transactions on Graphics in 2015 [12] (proceedings of SIGGRAPH Asia 2015).

Figure 3. Left. A chair automatically synthesized from a load scenario and an example pattern. The rigidity of the chair is within controlled bounds of a shape optimized without appearance objective. Right. A table design automatically synthesized.