Browsing by Author "Zhang, Yanci"

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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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    A Real-Time Adaptive Ray Marching Method for Particle-Based Fluid Surface Reconstruction
    (The Eurographics Association, 2022) Wu, Tong; Zhou, Zhiqiang; Wang, Anlan; Gong, Yuning; Zhang, Yanci; Ghosh, Abhijeet; Wei, Li-Yi
    In the rendering of particle-based fluids, the surfaces reconstructed by ray marching techniques contain more details than screen space filtering methods. However, the ray marching process is quite time-consuming because it needs a large number of steps for each ray. In this paper, we introduce an adaptive ray marching method to construct high-quality fluid surfaces in real-time. In order to reduce the number of ray marching steps, we propose a new data structure called binary density grid so that our ray marching method is capable of adaptively adjusting the step length. We also classify the fluid particles into two categories, i.e. high-density aggregations and low-density splashes. Based on this classification, two depth maps are generated to quickly provide the accurate start and approximated stop points of ray marching. In addition to reduce the number of marching steps, we also propose a method to adaptively determine the number of rays cast for different screen regions. And finally, in order to improve the quality of reconstructed surfaces, we present a method to adaptively blending the normal vectors computed from screen and object space. With the various adaptive optimizations mentioned above, our method can reconstruct high-quality fluid surfaces in real time.
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    A Second-Order Explicit Pressure Projection Method for Eulerian Fluid Simulation
    (The Eurographics Association and John Wiley & Sons Ltd., 2022) Jiang, Junwei; Shen, Xiangda; Gong, Yuning; Fan, Zeng; Liu, Yanli; Xing, Guanyu; Ren, Xiaohua; Zhang, Yanci; Dominik L. Michels; Soeren Pirk
    In this paper, we propose a novel second-order explicit midpoint method to address the issue of energy loss and vorticity dissipation in Eulerian fluid simulation. The basic idea is to explicitly compute the pressure gradient at the middle time of each time step and apply it to the velocity field after advection. Theoretically, our solver can achieve higher accuracy than the first-order solvers at similar computational cost. On the other hand, our method is twice and even faster than the implicit second-order solvers at the cost of a small loss of accuracy. We have carried out a large number of 2D, 3D and numerical experiments to verify the effectiveness and availability of our algorithm.