Browsing by Author "Qin, Hong"

Now showing 1 - 8 of 8
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    3D-CariNet: End-to-end 3D Caricature Generation from Natural Face Images with Differentiable Renderer
    (The Eurographics Association, 2021) Huang, Meijia; Dai, Ju; Pan, Junjun; Bai, Junxuan; Qin, Hong; Lee, Sung-Hee and Zollmann, Stefanie and Okabe, Makoto and Wünsche, Burkhard
    Caricatures are an artistic representation of human faces to express satire and humor. Caricature generation of human faces is a hotspot in CG research. Previous work mainly focuses on 2D caricatures generation from face photos or 3D caricature reconstruction from caricature images. In this paper, we propose a novel end-to-end method to directly generate personalized 3D caricatures from a single natural face image. It can create not only exaggerated geometric shapes, but also heterogeneous texture styles. Firstly, we construct a synthetic dataset containing matched data pairs composed of face photos, caricature images, and 3D caricatures. Then, we design a graph convolutional autoencoder to build a non-linear colored mesh model to learn the shape and texture of 3D caricatures. To make the network end-to-end trainable, we incorporate a differentiable renderer to render 3D caricatures into caricature images inversely. Experiments demonstrate that our method can achieve 3D caricature generation with various texture styles from face images while maintaining personality characteristics.
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    Accelerating Liquid Simulation With an Improved Data‐Driven Method
    (© 2020 Eurographics ‐ The European Association for Computer Graphics and John Wiley & Sons Ltd, 2020) Gao, Yang; Zhang, Quancheng; Li, Shuai; Hao, Aimin; Qin, Hong; Benes, Bedrich and Hauser, Helwig
    In physics‐based liquid simulation for graphics applications, pressure projection consumes a significant amount of computational time and is frequently the bottleneck of the computational efficiency. How to rapidly apply the pressure projection and at the same time how to accurately capture the liquid geometry are always among the most popular topics in the current research trend in liquid simulations. In this paper, we incorporate an artificial neural network into the simulation pipeline for handling the tricky projection step for liquid animation. Compared with the previous neural‐network‐based works for gas flows, this paper advocates new advances in the composition of representative features as well as the loss functions in order to facilitate fluid simulation with free‐surface boundary. Specifically, we choose both the velocity and the level‐set function as the additional representation of the fluid states, which allows not only the motion but also the boundary position to be considered in the neural network solver. Meanwhile, we use the divergence error in the loss function to further emulate the lifelike behaviours of liquid. With these arrangements, our method could greatly accelerate the pressure projection step in liquid simulation, while maintaining fairly convincing visual results. Additionally, our neutral network performs well when being applied to new scene synthesis even with varied boundaries or scales.
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    Human Motion Synthesis and Control via Contextual Manifold Embedding
    (The Eurographics Association, 2021) Zeng, Rui; Dai, Ju; Bai, Junxuan; Pan, Junjun; Qin, Hong; Lee, Sung-Hee and Zollmann, Stefanie and Okabe, Makoto and Wünsche, Burkhard
    Modeling motion dynamics for precise and rapid control by deterministic data-driven models is challenging due to the natural randomness of human motion. To address it, we propose a novel framework for continuous motion control by probabilistic latent variable models. The control is implemented by recurrently querying between historical and target motion states rather than exact motion data. Our model takes a conditional encoder-decoder form in two stages. Firstly, we utilize Gaussian Process Latent Variable Model (GPLVM) to project motion poses to a compact latent manifold. Motion states could be clearly recognized by analyzing on the manifold, such as walking phase and forwarding velocity. Secondly, taking manifold as prior, a Recurrent Neural Network (RNN) encoder makes temporal latent prediction from the previous and control states. An attention module then morphs the prediction by measuring latent similarities to control states and predicted states, thus dynamically preserving contextual consistency. In the end, the GP decoder reconstructs motion states back to motion frames. Experiments on walking datasets show that our model is able to maintain motion states autoregressively while performing rapid and smooth transitions for the control.
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    Inverse Modelling of Incompressible Gas Flow in Subspace
    (© 2017 The Eurographics Association and John Wiley & Sons Ltd., 2017) Zhai, Xiao; Hou, Fei; Qin, Hong; Hao, Aimin; Chen, Min and Zhang, Hao (Richard)
    This paper advocates a novel method for modelling physically realistic flow from captured incompressible gas sequence via modal analysis in frequency‐constrained subspace. Our analytical tool is uniquely founded upon empirical mode decomposition (EMD) and modal reduction for fluids, which are seamlessly integrated towards a powerful, style‐controllable flow modelling approach. We first extend EMD, which is capable of processing 1D time series but has shown inadequacies for 3D graphics earlier, to fit gas flows in 3D. Next, frequency components from EMD are adopted as candidate vectors for bases of modal reduction. The prerequisite parameters of the Navier–Stokes equations are then optimized to inversely model the physically realistic flow in the frequency‐constrained subspace. The estimated parameters can be utilized for re‐simulation, or be altered toward fluid editing. Our novel inverse‐modelling technique produces real‐time gas sequences after precomputation, and is convenient to couple with other methods for visual enhancement and/or special visual effects. We integrate our new modelling tool with a state‐of‐the‐art fluid capturing approach, forming a complete pipeline from real‐world fluid to flow re‐simulation and editing for various graphics applications.This paper advocates a novel method for modelling physically realistic flow from captured incompressible gas sequence via modal analysis in frequency‐constrained subspace. Our analytical tool is uniquely founded upon empirical mode decomposition (EMD) and modal reduction for fluids, which are seamlessly integrated towards a powerful, style‐controllable flow modelling approach.
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    A Novel Plastic Phase-Field Method for Ductile Fracture with GPU Optimization
    (The Eurographics Association and John Wiley & Sons Ltd., 2020) Zhao, Zipeng; Huang, Kemeng; Li, Chen; Wang, Changbo; Qin, Hong; Eisemann, Elmar and Jacobson, Alec and Zhang, Fang-Lue
    efficiently simulate ductile fracture with GPU optimization. At the theoretical level of physically-based modeling and simulation, our PPF approach assumes the fracture sensitivity of the material increases with the plastic strain accumulation. As a result, we first develop a hardening-related fracture toughness function towards phase-field evolution. Second, we follow the associative flow rule and adopt a novel degraded von Mises yield criterion. In this way, we establish the tight coupling of the phase-field and plastic treatment, with which our PPF method can present distinct elastoplasticity, necking, and fracture characteristics during ductile fracture simulation. At the numerical level towards GPU optimization, we further devise an advanced parallel framework, which takes the full advantages of hierarchical architecture. Our strategy dramatically enhances the computational efficiency of preprocessing and phase-field evolution for our PPF with the material point method (MPM). Based on our extensive experiments on a variety of benchmarks, our novel method's performance gain can reach 1.56x speedup of the primary GPU MPM. Finally, our comprehensive simulation results have confirmed that this new PPF method can efficiently and realistically simulate complex ductile fracture phenomena in 3D interactive graphics and animation.
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    A Rapid, End‐to‐end, Generative Model for Gaseous Phenomena from Limited Views
    (© 2021 Eurographics ‐ The European Association for Computer Graphics and John Wiley & Sons Ltd, 2021) Qiu, Sheng; Li, Chen; Wang, Changbo; Qin, Hong; Benes, Bedrich and Hauser, Helwig
    Despite the rapid development and proliferation of computer graphics hardware devices for scene capture in the most recent decade, the high‐resolution 3D/4D acquisition of gaseous scenes (e.g., smokes) in real time remains technically challenging in graphics research nowadays. In this paper, we explore a hybrid approach to simultaneously taking advantage of both the model‐centric method and the data‐driven method. Specifically, this paper develops a novel conditional generative model to rapidly reconstruct the temporal density and velocity fields of gaseous phenomena based on the sequence of two projection views. With the data‐driven method, we can achieve the strong coupling of density update and the estimation of flow motion, as a result, we can greatly improve the reconstruction performance for smoke scenes. First, we employ a conditional generative network to generate the initial density field from input projection views and estimate the flow motion based on the adjacent frames. Second, we utilize the differentiable advection layer and design a velocity estimation network with the long‐term mechanism to help achieve the end‐to‐end training and more stable graphics effects. Third, we can re‐simulate the input scene with flexible coupling effects based on the estimated velocity field subject to artists' guidance or user interaction. Moreover, our generative model could accommodate single projection view as input. In practice, more input projection views are enabling and facilitating the high‐fidelity reconstruction with more realistic and finer details. We have conducted extensive experiments to confirm the effectiveness, efficiency, and robustness of our new method compared with the previous state‐of‐the‐art techniques.
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    RegionSketch: Interactive and Rapid Creation of 3D Models with Rich Details
    (The Eurographics Association, 2019) Liu, Shuai; Hou, Fei; Hao, Aimin; Qin, Hong; Lee, Jehee and Theobalt, Christian and Wetzstein, Gordon
    In this paper, we articulate a new approach to interactive generation of 3D models with rich details by way of sketching sparse 2D strokes. Our novel method is a natural extension of Poisson vector graphics (PVG). We design new algorithms that distinguish themselves from other existing sketch-based design systems with three unique features: (1) A novel sketch metaphor to create freeform surface based on Poisson's equation, which is simple, intuitive, and free of ambiguity; (2) Convenient and flexible user interface that affords the user to add rich details to the surface with simple sketch input; and (3) Rapid model creation with sparse strokes, which enables novice users to enjoy the utilities of our system to create expected 3D models. We validate the proposed method through a large repository of interactively sketched examples. Our experiments and produced results confirm that our new method is a simple yet efficient design tool for modeling free-form shapes with simple and intuitive 2D sketches input.
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    Robust and Efficient SPH Simulation for High-speed Fluids with the Dynamic Particle Partitioning Method
    (The Eurographics Association, 2018) Zheng, Zhong; Gao, Yang; Li, Shuai; Qin, Hong; Hao, Aimin; Fu, Hongbo and Ghosh, Abhijeet and Kopf, Johannes
    In this paper, our research efforts are devoted to the efficiency issue of the SPH simulation when the ratio of velocities among fluid particles is large. Specifically, we introduce a k-means clustering method into the SPH framework to dynamically partition fluid particles into two disjoint groups based on their velocities, we then use a two-scale time step scheme for these two types of particles. The smaller time steps are for particles with higher speed in order to preserve temporal details and guarantee the numerical stability. In contrast, the larger time steps are used for particles with smaller speeds to reduce the computational expense, and both types of particles are tightly coupled in the simulation.We conduct various experiments which have manifested the advantages of our methods over the conventional SPH technique and its new variants in terms of efficiency and stability.