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    Characterisation of Position Based Dynamics for Elastic Materials
    (The Eurographics Association, 2016) Rodero, Cristóbal; Real, Pablo; Zuñeda, Pedro; Monteagudo, Carlos; Lozano, Miguel; García-Fernández, Ignacio; Alejandro Garcia-Alonso and Belen Masia
    Position Based Dynamics (PBD) methodology is a widely used approach for simulation of deformable bodies in the context of video games. Its main advantages over force based methods are its unconditional stability and its constraint based approach. However, it does not involve physically inspired parameters and its behaviour depends on time step size. This makes it difficult to reproduce a given elastic behaviour. In this work we perform an analysis of the mechanical properties in a PBD elastic system, and compare it to the Finite Element Method (FEM). We propose a methodology to fit the parameters of PBD to simulate a particular Young's modulus and Poisson's ratio.
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    Phase Space Data-Driven Simulation of Elastic Materials
    (The Eurographics Association, 2016) Monteagudo, Carlos; Lozano, Miguel; García-Fernández, Ignacio; Martinez-Gil, Francisco; Alejandro Garcia-Alonso and Belen Masia
    The use of data driven models in computer animation offers several benefits. We present an analysis of a regression model as a method to simulate cloth. In our approach, we generate data from a simple mass-spring system and we fit a regressor. Then, we assemble more complex mass-spring systems and use the learnt model to simulate them. To validate the approach we perform several tests. We analyze the elastic properties of a single learnt spring, measuring its stiffness coefficient, and compare it to the original, physics-based, model. We also build several test scenarios which include the simulation of a piece of cloth under gravity, comparing the regression model and the physics-based model. Finally we test the behaviour of the regression model for systems with high stiffness coefficient and compare its stability properties with a semi-implicit Euler integration method.