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  • PhD Defense- Hongyi Xu

    Thu, Apr 20, 2017 @ 12:00 PM - 02:00 PM

    Computer Science

    University Calendar

    PhD Candidate: Hongyi Xu

    Title: Interactive Material and Damping Design.

    Date: 04/20/17
    Time: 12-2pm
    Location: SAL 213


    Jernej Barbic (Chair)
    Hao Li
    Yong Chen (Outside)


    Finite Element Method (FEM) has been widely used for simulations of three-dimensional deformable objects. To produce compelling and artist-controllable FEM dynamics, the choices of material elasticity and damping properties are critically important. This thesis presents an intuitive and interactive design method to explore the high-dimensional space of material and damping for use in FEM simulations in computer graphics, animation and related fields.

    This thesis first demonstrates how to intuitively explore the space of isotropic and anisotropic nonlinear materials, for design of FEM animations. Previous applications of nonlinear solid elasticity employed materials from a few standard families such as linear corotational, nonlinear St.Venant-Kirchhoff and Neo-Hookean material. However, the spaces of all nonlinear isotropic and anisotropic materials are infinite-dimensional and much broader than these standard materials. We simplify this infinite-dimensional material space with the Valansis-Landel hypothesis and demonstrate how to easily design arbitrary isotropic and anisotropic nonlinear elasticity with local control, using a spline interface. Our materials accelerate simulation design and enable visual effects that are difficult or impossible to achieve with standard nonlinear materials.

    Material properties may vary across the volume of the object, producing heterogeneous deformable behaviors. My thesis presents an interactive inverse method to design heterogeneous material distributions, which conform to prescribed displacements and internal elastic forces at a few selected positions. However, this optimization problem is high-dimensional and solving it in the full space is not practical for interactive design. We demonstrate scalability to complex examples using a novel model reduction of the material space, which accelerates the optimization by two orders of magnitude and makes the convergence much more robust.

    FEM dynamics is largely affected also by the damping properties, in addition to elasticity. This thesis gives 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 independent user-prescribed amount, achieving anisotropic damping effects. Similar to our spline-based elasticity, we also achieve nonlinear damping that depends on the example deformation magnitudes, by editing a single spline curve for each example. The nonlinear damping curves can also be automatically inferred from high-level user inputs, such as the amount of amplitude loss in one oscillation cycle. Our method enables an artist-directable and intuitive approach to controlling nonlinear and anisotropic damping, which can generate effects not possible with previous methods and better capture real-world damping dynamics

    Location: Henry Salvatori Computer Science Center (SAL) - 213

    Audiences: Everyone Is Invited

    Contact: Lizsl De Leon


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