Browsing by Author "He, Xiaowei"

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    Biorthogonal Wavelet Surface Reconstruction Using Partial Integrations
    (The Eurographics Association and John Wiley & Sons Ltd., 2018) Ren, Xiaohua; Lyu, Luan; He, Xiaowei; Cao, Wei; Yang, Zhixin; Sheng, Bin; Zhang, Yanci; Wu, Enhua; Fu, Hongbo and Ghosh, Abhijeet and Kopf, Johannes
    We introduce a new biorthogonal wavelet approach to creating a water-tight surface defined by an implicit function, from a finite set of oriented points. Our approach aims at addressing problems with previous wavelet methods which are not resilient to missing or nonuniformly sampled data. To address the problems, our approach has two key elements. First, by applying a three-dimensional partial integration, we derive a new integral formula to compute the wavelet coefficients without requiring the implicit function to be an indicator function. It can be shown that the previously used formula is a special case of our formula when the integrated function is an indicator function. Second, a simple yet general method is proposed to construct smooth wavelets with small support. With our method, a family of wavelets can be constructed with the same support size as previously used wavelets while having one more degree of continuity. Experiments show that our approach can robustly produce results comparable to those produced by the Fourier and Poisson methods, regardless of the input data being noisy, missing or nonuniform. Moreover, our approach does not need to compute global integrals or solve large linear systems.
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    Reformulating Hyperelastic Materials with Peridynamic Modeling
    (The Eurographics Association and John Wiley & Sons Ltd., 2018) Xu, Liyou; He, Xiaowei; Chen, Wei; Li, Sheng; Wang, Guoping; Fu, Hongbo and Ghosh, Abhijeet and Kopf, Johannes
    Peridynamics is a formulation of the classical elastic theory that is targeted at simulating deformable objects with discontinuities, especially fractures. Till now, there are few studies that have been focused on how to model general hyperelastic materials with peridynamics. In this paper, we target at proposing a general strain energy function of hyperelastic materials for peridynamics. To get an intuitive model that can be easily controlled, we formulate the strain energy density function as a function parameterized by the dilatation and bond stretches, which can be decomposed into multiple one-dimensional functions independently. To account for nonlinear material behaviors, we also propose a set of nonlinear basis functions to help design a nonlinear strain energy function more easily. For an anisotropic material, we additionally introduce an anisotropic kernel to control the elastic behavior for each bond independently. Experiments show that our model is flexible enough to approximately regenerate various hyperelastic materials in classical elastic theory, including St.Venant-Kirchhoff and Neo-Hookean materials.
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    Semi-analytical Solid Boundary Conditions for Free Surface Flows
    (The Eurographics Association and John Wiley & Sons Ltd., 2020) Chang, Yue; Liu, Shusen; He, Xiaowei; Li, Sheng; Wang, Guoping; Eisemann, Elmar and Jacobson, Alec and Zhang, Fang-Lue
    The treatment of solid boundary conditions remains one of the most challenging parts in the SPH method. We present a semianalytical approach to handle complex solid boundaries of arbitrary shape. Instead of calculating a renormalizing factor for the particle near the boundary, we propose to calculate the volume integral inside the solid boundary under the local spherical frame of a particle. By converting the volume integral into a surface integral, a computer aided design (CAD) mesh file representing the boundary can be naturally integrated for particle simulations. To accelerate the search for a particle's neighboring triangles, a uniform grid is applied to store indices of intersecting triangles. The new semi-analytical solid boundary handling approach is integrated into a position-based method [MM13] as well as a projection-based [HWW*20] to demonstrate its effectiveness in handling complex boundaries. Experiments show that our method is able to achieve comparable results with those simulated using ghost particles. In addition, since our method requires no boundary particles for deforming surfaces, our method is flexible enough to handle complex solid boundaries, including sharp corners and shells.