Data-driven elastic models for cloth

Figure 1: Design of isotropic nonlinear materials: The soft-body motion of the wrestler was computed using FEM, constrained to a motion capture skeletal dancing animation. Using our method, we designed a nonlinear isotropic material that performs well both during impulsive and gentle animation phases. Top row: the wrestler is performing high jumps. The soft Neo-Hookean material exhibits artifacts (belly, thighs) when the character moves abruptly. Our material and the stiff Neo-Hookean material produce good deformations. Bottom row: deformations during a gentle phase (walking while dancing) of the same motion sequence. The soft Neo-Hookean material and our method produce rich small-deformation dynamics, whereas the stiff Neo-Hookean material inhibits it. The Young's modulus of material (a) was chosen to produce good dynamics during gentle motion. We then edited it to address impulsive motion, producing (c). The stiff material in (b) is the best matching material to (c) among Neo-Hookean materials, minimizing the L 2 material curve difference to (c). AbstractThe Finite Element Method is widely used for solid deformable object simulation in film, computer games, virtual reality and medicine. Previous applications of nonlinear solid elasticity employed materials from a few standard families such as linear corotational, nonlinear St.Venant-Kirchhoff, Neo-Hookean, Ogden or Mooney-Rivlin materials. However, the spaces of all nonlinear isotropic and anisotropic materials are infinite-dimensional and much broader than these standard materials. In this paper, we demonstrate how to intuitively explore the space of isotropic and anisotropic nonlinear materials, for design of animations in computer graphics and related fields. In order to do so, we first formulate the internal elastic forces and tangent stiffness matrices in the space of the principal stretches of the material. We then demonstrate how to design new isotropic materials by editing a single stress-strain curve, using a spline interface. Similarly, anisotropic (orthotropic) materials can be designed by editing three curves, one for each material direction. We demonstrate that modifying these curves using our proposed interface has an intuitive, visual, effect on the simulation. Our materials accelerate simulation design and enable visual effects that are difficult or impossible to achieve with standard nonlinear materials.

Section: Related Workmentioning

confidence: 99%

Nonlinear material design using principal stretches

Sin

Zhu

et al. 2015

“…To circumvent the complexity of parameter tuning, several authors obtain material parameters by measuring real objects. Methods have been proposed to estimate Young's modulus and/or Poisson's ratio [Schnur and Zabaras 1992;Becker and Teschner 2007;Lee and Lin 2012], cloth stretch and bending parameters [Wang et al 2011], facial muscle activations [Sifakis et al 2005], viscoelastic properties [Kauer et al 2002;Gao et al 2009], or plasticity parameters [Kajberg and Lindkvist 2004]. Bickel et al [2009] acquired heterogeneous material distributions of real objects through force and displacement measurements, followed by high-dimensional material optimization of Young's moduli for all the tetrahedra.…”

Section: Related Workmentioning

confidence: 99%

Interactive Material Design Using Model Reduction

Chen

et al. 2015

We demonstrate an interactive method to create heterogeneous continuous deformable materials on complex three-dimensional meshes. The user specifies displacements and internal elastic forces at a chosen set of mesh vertices. Our system then rapidly solves an optimization problem to compute a corresponding heterogeneous spatial distribution of material properties using the Finite Element Method (FEM) analysis. We apply our method to linear and nonlinear isotropic deformable materials. We demonstrate that solving the problem interactively in the full-dimensional space of individual tetrahedron material values is not practical. Instead, we propose a new model reduction method that projects the material space to a low-dimensional space of material modes. Our model reduction accelerates optimization by two orders of magnitude and makes the convergence much more robust, making it possible to interactively design material distributions on complex meshes. We apply our method to precise control of contact forces and control of pressure over large contact areas between rigid and deformable objects for ergonomics. Our tetrahedron-based dithering method can efficiently convert continuous material distributions into discrete ones and we demonstrate its precision via FEM simulation. We physically display our distributions using haptics, as well as demonstrate how haptics can aid in the material design. The produced heterogeneous material distributions can also be used in computer animation applications.

“…Relevant works include the design of nonlinear parametric models [Volino et al 2009], estimation of material coefficients from force and deformation examples [Wang et al 2011;Miguel et al 2012], and design of internal friction models to capture cloth hysteresis [Miguel et al 2013]. …”

Section: Related Workmentioning

confidence: 99%

“…Visually interesting effects such as detailed tearing, snags, or loose yarn ends require modeling individual yarns. Moreover, yarn-based models can constitute the cornerstone to develop accurate solutions to large-scale cloth simulation, revealing the nonlinearities and complex interplays measured in real fabrics [Wang et al 2011;Miguel et al 2012;Miguel et al 2013].…”

Section: Introductionmentioning

confidence: 99%

Yarn-level simulation of woven cloth

Cirio¹,

López‐Moreno²,

Miraut³

et al. 2014

109

110

Figure 1: Yarn-level simulation of a shirt with 2023 yarns and 350530 crossing nodes. We produce a snag on the shirt by pulling on a seam node. Fine-scale deformations showing yarn sliding and thin wrinkles are combined with large-scale motion of the shirt. AbstractThe large-scale mechanical behavior of woven cloth is determined by the mechanical properties of the yarns, the weave pattern, and frictional contact between yarns. Using standard simulation methods for elastic rod models and yarn-yarn contact handling, the simulation of woven garments at realistic yarn densities is deemed intractable. This paper introduces an efficient solution for simulating woven cloth at the yarn level. Central to our solution is a novel discretization of interlaced yarns based on yarn crossings and yarn sliding, which allows modeling yarn-yarn contact implicitly, avoiding contact handling at yarn crossings altogether. Combined with models for internal yarn forces and inter-yarn frictional contact, as well as a massively parallel solver, we are able to simulate garments with hundreds of thousands of yarn crossings at practical framerates on a desktop machine, showing combinations of large-scale and fine-scale effects induced by yarn-level mechanics.