Browsing by Author "Coros, Stelian"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Robust and Artefact-Free Deformable Contact with Smooth Surface Representations
    (The Eurographics Association and John Wiley & Sons Ltd., 2024) Du, Yinwei; Li, Yue; Coros, Stelian; Thomaszewski, Bernhard; Skouras, Melina; Wang, He
    Modeling contact between deformable solids is a fundamental problem in computer animation, mechanical design, and robotics. Existing methods based on C0-discretizations-piece-wise linear or polynomial surfaces-suffer from discontinuities and irregularities in tangential contact forces, which can significantly affect simulation outcomes and even prevent convergence. In this work, we show that these limitations can be overcome with a smooth surface representation based on Implicit Moving Least Squares (IMLS). In particular, we propose a self collision detection scheme tailored to IMLS surfaces that enables robust and efficient handling of challenging self contacts. Through a series of test cases, we show that our approach offers advantages over existing methods in terms of accuracy and robustness for both forward and inverse problems.
  • Thumbnail Image
    Item
    A Second Order Cone Programming Approach for Simulating Biphasic Materials
    (The Eurographics Association and John Wiley & Sons Ltd., 2022) Tang, Pengbin; Coros, Stelian; Thomaszewski, Bernhard; Dominik L. Michels; Soeren Pirk
    Strain limiting is a widely used approach for simulating biphasic materials such as woven textiles and biological tissue that exhibit a soft elastic regime followed by a hard deformation limit. However, existing methods are either based on slowly converging local iterations, or offer no guarantees on convergence. In this work, we propose a new approach to strain limiting based on second order cone programming (SOCP). Our work is based on the key insight that upper bounds on per-triangle deformations lead to convex quadratic inequality constraints. Though nonlinear, these constraints can be reformulated as inclusion conditions on convex sets, leading to a second order cone programming problem-a convex optimization problem that a) is guaranteed to have a unique solution and b) allows us to leverage efficient conic programming solvers. We first cast strain limiting with anisotropic bounds on stretching as a quadratically constrained quadratic program (QCQP), then show how this QCQP can be mapped to a second order cone programming problem. We further propose a constraint reflection scheme and empirically show that it exhibits superior energy-preservation properties compared to conventional end-of-step projection methods. Finally, we demonstrate our prototype implementation on a set of examples and illustrate how different deformation limits can be used to model a wide range of material behaviors.