Simulating Cloth at the Computer

The intent of the present talk is to introduce cloth modelling, as an area of increasing interest for computer graphics and CAD modelling applications. Drapes and garments are, in fact, visualization elements recurrently appearing in animated movies and videogames, or virtual reality scenes (e.g., virtual catwalks). Besides, a strong impulse comes from industry, e.g. for apparel, upholstery and fabric furniture production, increasingly demanding CAD tools driving the process of cloth design.
A survey on some famous cloth models proposed by the computer graphics community is presented. While purely geometric cloth models can be adequate for animation tasks, discrete or continuous physical formulations need to be used to accurately predict cloth shape behaviour for simulation purposes, e.g. functional analysis, virtual cloth prototyping, etc. We particularly focus on physics-based approaches, taking into account structural global properties depending on the considered textile materials, as well as interactions with the external environment. Some continuous PDE formulations inherited by structural mechanics approaches have been proposed in the literature, more convenient under static conditions and small displacements. However, differently from continuous textile engineering approaches, computer graphics’ community involved in physics-based cloth modelling tends to prefer discrete ODE models, typically formulated through Lagrangian or Newtonian dynamics, formally simpler and computationally less expensive. Particle-based models are the most frequently considered discrete cloth representations. These are, somehow, a coherent representation of the intrinsic “discrete” nature of textiles as interlaced plots of threads, particularly efficient for global shape visualization/simulation under dynamic conditions and large cloth deformations. The main characteristics and some numerical issues around particle-based cloth modelling are singled out.
As an application, we present some results on discrete physics-based cloth modelling and simulation, as obtained by the KAEMaRT group of Dipartimento di Meccanica, Politecnico di Milano and Dipartimento di Ingegneria Industriale, Università di Parma. Our research is aiming to extend a particle-based Newtonian cloth model originally proposed for simple cloth geometries to complex-shaped textile configurations such as garments or functional textiles, presenting several levels of design complexities (e.g., multi-layered fabric composition, seams and other construction constraints, etc.) for CAD design, simulation and virtual prototyping purposes. Examples and test cases are shown.