Unified Visualization of 4D Particle System and Scalar Fields by Extending Point-Based Rendering

数学流体建模一般分为两大类：欧拉和拉格朗日。前者通过定义相关的物理场来表述流体的行为，后者将流体视为一组粒子来解决多体问题。这两种方法伴随着不同的可视化方案：表面渲染（欧拉式）和基于点的渲染（拉格朗日式）。同时，混合仿真最近被用来将这两种方法结合起来描述许多科学和工程问题中出现的复杂现象。因此，迫切需要建立连续和不连续对象的同时呈现。Pfister等人在2000年提出了一种新的建模技术，称为surfels（表面细胞），它依赖于基于点的近似来呈现刚体表面的复杂形状。在本研究中，我们通过添加诸如半径和不透明度分布等特征来描述冲浪原语的磁盘，从而将这一概念扩展到对分散物体的可视化，从而产生一个表示物理场和粒子系统的统一框架。然后在标准工作站上实现了一个原型渲染系统，该系统可以执行表面渲染、体积渲染和粒子渲染等所有传统技术，并通过以下两个具体问题验证了其可行性：(1)地层处置数据集（数据由富士研究所提供）使用基于粒子的模型来模拟核废料长期渗透到多孔介质中的过程。通过使用我们的系统，200,000个半径相对较小的分散分布的胶体冲浪板自然地叠加在重叠的冲浪板上，以可视化多孔介质的内部边界。(2)破碎波数据集（数据由东京大学S.Koshizuka提供）破碎波仍然是自然现象交互式图像合成研究中具有挑战性的课题之一。在我们的研究中，采用运动粒子半隐式方法对二维破碎波的动力学进行了建模。然后，采用并行插值和局部粒子生成的方法生成准三维破碎波数据集；我们充分利用了具有不同半径和高斯不透明度分布的扩展冲浪原语，以一致的方式可视化破碎波的组成部分，即膨胀、波纹和飞溅。少

Mathematical fluid modeling is generally divided into two major categories : Eulerian and Lagrangian. The former formulates the fluid behavior by defining related physical fields, whereas the latter regards the fluid as a set of particles to solve the multiple body problem. The two approaches are accompanied with different visualization schemes : that is surface rendering (Eulerian) and point-based rendering (Lagranian). Meanwhile, hybrid simulation has recently been exploited to couple these two approaches for describing complex phenomena arising in many science and engineering problems. Therefore, there is an urgent need to establish simultaneous rendering of continuous and discontinuous objects.Pfister et al. proposed in 2000, a novel modeling technique, called surfels (surface cells), which relies on a point-based approximation to render complex shape of rigid body surfaces. In this study, we have extended the concept to visualize scattered objects as well by adding such features a … More s the radius and opacity distribution to describe the disk of surfel primitives, to yield a unified framework for representing physical fields and particle system. Then a prototype rendering system has been implemented on a standard workstation, where all of the traditional techniques such as surface rendering, volume rendering and particle rendering can be executed, and its feasibility has been proven with application to the following two specific problems :(1)Stratum disposal dataset (data courtesy of Fuji Research Institute)A particle-based model was used to simulate how nuclear waste infiltrate into a porous media over the long term. By using our system, scattered distribution of 200,000 colloid surfels with a relatively small radius is superimposed naturally on overlapped surfels to visualize inner boundaries of the porous media.(2)Breaking wave dataset (data coutesy of S.Koshizuka, University of Tokyo)Breaking wave is still known as one of the challenging topics in the research on interactive image synthesis of natural phenomena. In our study, the dynamics of 2D breaking wave was modeled using the Moving Particle Semi-implicit method. Then, a quasi-3D dataset of breaking wave was generated with parallel interpolation and local particle generation. We took full advantage of extended surfel primitives with varying radius and Gaussian opacity distribution to visualize the components of breaking waves, namely swell and riffle as well as splash, in a consistent manner. Less