. Nonlinear anisotropic damping that matches real-world leaf motion. We experimentally estimated both the leaf elastic nonlinear material, and our nonlinear damping model, to match the real-world ground truth leaf motion. Our model accommodates anisotropic nonlinear damping, with di erent nonlinear damping properties for the leaf bending in the up-down (deformation 1) and le -right directions (deformation 2). To date, material modeling in physically based computer animation has largely focused on mass and sti ness material properties. However, deformation dynamics is largely a ected also by the damping properties. In this paper, we propose an interactive design method for nonlinear isotropic and anisotropic damping of complex three-dimensional solids simulated using the Finite Element Method (FEM). We rst give a damping design method and interface whereby the user can set the damping properties so that motion aligned with each of a few chosen example deformations is damped by an independently prescribed amount, whereas the rest of the deformation space follows standard Rayleigh damping, or any viscous damping. Next, we demonstrate how to design nonlinear damping that depends on the magnitude of the deformation along each example deformation, by editing a single spline curve for each example deformation. Our user interface enables an artdirected and intuitive approach to controlling damping in solid simulations. We mathematically prove that our nonlinear anisotropic damping generalizes the frequency-dependent Caughey damping model, when starting from the Rayleigh damping. Finally, we give an inverse design method whereby the damping curve parameters can be inferred automatically from high-level user input, such as the amount of amplitude loss in one oscillation cycle along each of the chosen example deformations. To minimize numerical damping for implicit integration, we introduce an accurate and stable implicit integrator, which removes spurious high-frequency oscillations while only introducing a minimal amount of numerical damping. Our damping This research was sponsored in part by the National Science Foundation (CAREER-1055035, IIS-1422869), and USC Annenberg Graduate Fellowship to Hongyi Xu. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for pro t or commercial advantage and that copies bear this notice and the full citation on the rst page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior speci c permission and/or a fee. Request permissions from permissions@acm.org. © 2017 ACM. 0730-0301/2017/7-ART53 $15.00 DOI: http://dx.doi.org/10.1145/3072959.3073631 can generate e ects not possible with previous methods, such as controllable nonlinear decaying envelopes whereby large deformations are damped faster or slower than small deformations, and damping anisotropic e ects. We also t our damping to videos of real-world objects undergoing large deformations, capturing their nonlinear and anisotropic damping dynamics.
Xu and Barbi c REF fine-tuned the damping model based on a few example deformations.
Example-based damping design
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Physics Computer Science