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基于多特征超分网络的布料褶皱合成

Multi-Feature Super-Resolution Network for Cloth Wrinkle Synthesis

  • 摘要: 1、研究背景(context):
    布料仿真在众多应用中起着重要的作用,如电影,视频游戏,虚拟试衣。物理仿真技术的飞速发展,使具有逼真细节的服装动画成为现实。但这些方法需要很高分辨率的网格来表示精细的细节,因此需要大量的计算来求解方程、解决碰撞问题。此外还需要大量的人力来调整仿真参数从而获得想要的褶皱形态。近期数据驱动的方法提供了快速且逼真的褶皱生成效果。依靠预先计算的数据和数据驱动技术,可以直接合成高分辨率网格,也可以通过物理模拟的低分辨率网格对其进行褶皱叠加。尽管如此,现有的数据驱动方法或依赖于人体姿势不适用于宽松服装,或缺乏对自由度较大的通用布料进行动态的褶皱建模。
    2、目的(Objective):该研究的目的是快速合成高质量且时序稳定的布料仿真动画,不仅能针对紧身衣,还能适应于更加宽松的服装或者通用布料,解决目前研究方法遇到的挑战。
    3、方法(Method):本文提出了多特征超分网络来进行布料的褶皱合成。通过虚拟弹簧约束和多分辨率动态模型同步模拟一对高低分辨率网格,使其在细节上有差异。然后将模拟的网格转换为双分辨率几何图像,编码位移、法相和速度特征。基于这些特征,本文设计了空间和时间损失函数来训练多特征超分网络,从而获得时序一致的几何图像。再将几何图像转换成三维网格即可快速获得稳定且富含细节的布料动画。
    4、结果(Result & Findings):
    本文构建了三个高低分辨率数据集并在数据集上进行了定量和定性对比,取得了最优的数值指标和最佳的视觉效果。通过对比和消融实验证明了本文提出的多特征及损失函数的价值。本文提出的方法以高帧速率得到逼真的布料动画:比传统的物理模拟快12~14倍。
    5、结论(Conclusions):
    本文提出了多特征框架合成布料动画细节。将三维网格的时空特征嵌入到多张图像中,共同学习超分辨网络,设计了基于运动学的损失,保证时序一致性。在数据构造时设计了同步仿真方法,不仅可以生成配对的三维衣服网格用于细节增强,也可以用于其他应用,如不同形状结构的三维形状匹配。就非配对数据的细节增强以及将该方法泛化到不同材质的服装上是未来进一步研究的方向。

     

    Abstract: Existing physical cloth simulators suffer from expensive computation and difficulties in tuning mechanical parameters to get desired wrinkling behaviors. Data-driven methods provide an alternative solution. They typically synthesize cloth animation at a much lower computational cost, and also create wrinkling effects that are similar to the training data. In this paper we propose a deep learning based method for synthesizing cloth animation with high resolution meshes. To do this we first create a dataset for training:a pair of low and high resolution meshes are simulated and their motions are synchronized. As a result the two meshes exhibit similar large-scale deformation but different small wrinkles. Each simulated mesh pair is then converted into a pair of low- and high-resolution "images" (a 2D array of samples), with each image pixel being interpreted as any of three descriptors:the displacement, the normal and the velocity. With these image pairs, we design a multi-feature super-resolution (MFSR) network that jointly trains an upsampling synthesizer for the three descriptors. The MFSR architecture consists of shared and task-specific layers to learn multi-level features when super-resolving three descriptors simultaneously. Frame-to-frame consistency is well maintained thanks to the proposed kinematics-based loss function. Our method achieves realistic results at high frame rates:12-14 times faster than traditional physical simulation. We demonstrate the performance of our method with various experimental scenes, including a dressed character with sophisticated collisions.

     

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