Appearance
We made significant progress towards efficiently simulating the appearance of an object by taking into account lower-scale material phenomena. In contrast to pigment-based colors – where spectral components of incident light are absorbed by the pigment material – structural colorization arises from the interaction of light with micro- and nanostructures. Designing such colorization is challenging, however, since the wave nature of light has to be taken into account. In the work of Auzinger et al. 2018, we present a computational design tool for the creation of transparent nanostructures with feature sizes in the range of 100s of nm that realize simple colorization of light transmitted through them. We take fabrication constraints of multiphoton lithography into account to ensure the feasibility of fabricating the designs.
We also investigated the reproduction of colored textured objects using polyjet 3D printing technology. Color texture reproduction in 3D printing is affected by volumetric light transport (cross-talk) between surface points on a 3D print, which can lead to significant blur of details and color bleeding. In Elek et al. 2021, we presented a practical measurement system for the materials light transport parameters. We counteract heterogeneous scattering to obtain the impression of a crisp albedo texture on top of the 3D print, by optimizing for a fully volumetric material distribution that preserves the target appearance (Elek et al. 2017). We evaluated our system using a five-tone 3D print process, demonstrating that our method preserves high-frequency features well without having to compromise on color gamut. In the follow-up work of Sumin et al. 2019, we designed a full-fledged optimization-based heuristic for arbitrary 3D shapes, and in Rittig et al. 2021, we replace the light transport simulation with a data-driven approach, allowing a speed up of two orders of magnitude while achieving results of similar quality.
Elastic behaviour
We made important steps towards modeling systems for designing large, heterogeneous elastic objects with higher-level functional behavior.
FlexMaps (Malomo et al. 2018) is a novel framework we developed for fabricating smooth shapes out of flat, flexible panels with tailored mechanical properties. For these panels, we design and obtain specific mechanical properties such that, once they are assembled, the static equilibrium configuration matches the desired 3D shape. We also studied the design space of plane elastic curves (Hafner et al. 2021) and cold bent glass panels (Gavriil et al. 2020). Closely connected to this work is self-actuated material and structure design. These types of structures are usually composed of an actuation mechanism and a deformation limiting mechanism that, when coupled together, produce the desired deformed shape. We have developed a computational approach for designing curvy shells that self-actuate from an initially flat state (Guseinov et al. 2020).
For reproducing digital objects, we developed a new technique for reusable elastic mold design (Alderighi et al. 2018). We realized an innovative formulation for how to place cuts in the mold volume to allow for cast extraction (Alderighi et al. 2019) and enabling the manufacturing of individual parts using two-piece reusable rigid molds (Alderighi et al. 2021).
We have also recently developed a general method for shape optimization of models that directly works on CAD model representations without the need of remeshing thanks to an underlying XFFEM approach (Hafner et al 2019).
Sensing
In Degraen et al. 2021, we investigate replicating the haptics of real materials and propose strategies for capturing and reproducing digitized textures to better resemble the perceived haptics of the originals.
Unified Simulation
Our goal was to develop a framework for multi-objective optimization and efficient design exploration. We developed a data-driven technique to instantly predict how fluid flows around various three-dimensional objects (Umetani et al. 2018). We demonstrate the effectiveness of our approach for the interactive design and optimization of a car body. Furthermore, we investigated the interactive design of functional mechanical objects that can be 3D printed (Zhang et al. 2017). We also made important progress towards an active control system for manufacturing with self-correcting behavior, employing reinforcement learning to dynamically adjusts the printing path and parameters.
