基于显微CT扫描的三维织物仿真

为了在纹织CAD中通过织物仿真减少产品的试织次数、降低生产成本,提出一种基于显微CT扫描的三维织物仿真方法.首先由显微CT扫描的纱线切片得到单根纱线的密度信息;然后根据真实纱线的彩色图像生成纱线的体数据模型;最后根据织物结构中经纬线的位置信息对纱线体数据进行变换和填充,得到织物的体数据模型并进行体绘制,获得真实感较强的仿真效果,可表现出纱线的毛羽、捻度等效果.实验结果表明,该方法切实可行,织物结果真实自然.     

机织物组织图的数学描述与3维几何建模

目的 织物组织结构的3维几何模型是进行机织物的3维外观模拟和性能预测的基础。提出直接由组织结构参数建立机织物3维几何模型的方法。方法 根据构成机织物组织交织规律的浮长序列、交叉数、飞数、经纬纱循环数等参数,建立单层织物的组织图矩阵生成的数学公式;结合组织图矩阵和织物中纱线的屈曲模型,采用直线和余弦曲线分段函数建立组织矩阵中组织点间纱线路径的数学公式,并基于椭圆截面模型实现机织物的3维模拟;通过对经、纬纱的X或Y坐标函数中引入修正因子,实现纱线路径的扭曲变形。结果 实现不同组织类别、不同结构参数、不同纱线截面及基于均匀分布的纱线扭曲等条件下单层机织物的3维几何结构模拟,仿真效果较好。结论 本文方法将组织图矩阵生成和织物结构3维建模两个过程结合,快速生成单层机织物的3维几何模型。通过实时更改结构参数,实现不同结构织物的模拟,而且可以模拟经、纬纱平面外扭曲现象。     

一种简易的织物表面外观模拟方法

在织物CAD系统中加入织物表面外观模拟功能,将极大地提高系统的性能,也是如今数码纺织时代对织物设计的新要求.本文先简要地介绍织物外观模拟系统的基本原理与总体结构,指出纱线外观和织物表面纱线交织结构是织物模拟中的两个重要因素.随后提出一个"三亮度色纱模型",用于表示纱线在织物中的形态,该模型简单,且易于实现,得到的效果良好.在这个模型基础上,叠加由Perlin噪声函数产生的毛羽纹理,生成带有毛羽的纱线外观.最后给出几个织物外观模拟的实例,并对本文进行了总结.     

基于PhysX物理引擎的布料仿真技术的研究与实现

运用布料仿真技术中的物理方法来实现对布料印制效果的三维展示.首先对布料建立弹簧-质点模型,分析弹簧-质点模型的受力状况,以牛顿第二定律作为理论基础,用PhysX物理引擎中的模拟函数模拟布料的运动,并解决了仿真中与刚体的碰撞问题与布料自身的碰撞问题.最后通过生成多个仿真效果和加入多种交互功能,构建了适用于印花图案设计产品的虚拟展厅.     

基于面料力学属性的三维织物模拟

为了精确再现虚拟服装中面料的力学属性,提出一种模拟不同材质织物变形效果的方法.首先测试样本的力学性能参数,通过相关性分析获得其中与悬垂特性密切相关的部分参数,以此作为神经网络的输入数据;然后对比实拍样本及其静态仿真效果图,将获得样本仿真模型控制参数的期望值作为BP神经网络的输出数据;最后建立BP神经网络实现织物力学属性与仿真模型控制参数之间的非线性映射.应用文中方法对15种常用服装面料进行实验的结果表明,仿真效果较好地体现了面料的材质信息,在此基础上实现的虚拟服装更加精准,有助于提高系统的真实感.     

基于DLA模型的花式纱线真实感模拟算法

主要研究了分形生长理论的基本模型——扩散有限凝聚（DLA）模型,分析并实现了DLA模型的计算机模拟方法,并对模型演变进行了讨论,得到了形式多样的凝聚效果。并且将DLA模型结合纱线和织物模拟相关技术和结论,用双侧线性DLA模型算法生成纱线毛羽模版,与基础纱线进行纹理合成,对纱线毛羽效果进行了较为真实的模拟。用这种方法能够较为逼真的反应出花式纱线不规则、随机多变且局部自相似的毛羽特征。     

基于改进的弹簧-质点模型的三维服装模拟

针对三维服装造型与效果仿真中存在的模型复杂、模拟效率低、忽略服装的结构特征等问题,提出了改进的弹簧-质点模型.利用该模型统一建立了2D→3D映射和服装真实感模拟方程,给出方程中质点所受内力和外力的组成与表达式以及动态系统的推导和求解过程,并且描述了模拟的具体实现算法.改进的弹簧-质点模型克服了原有模型对服装织物的材料性能表达单一的缺点,考虑了拉伸、剪切、弯曲等力学性能以及省/褶等结构因素对服装外观的影响,实现了较复杂的服装外型.通过从效率与效果两个方面与其他模拟系统进行比较,发现该技术的模拟效率较高而且模拟结果较为真实.该模拟技术已经在服装企业推广应用,用户反映良好.     

基于改进质点弹簧模型下的布料实时仿真

布料模拟一直是计算机动画的研究热点.且对于虚拟现实技术有着重要意义.在以往的研究中,人们提出了许多模拟织物运动的方法,方法的一个主要缺点是复杂度高、计算效率低,无法满足交互设计和实时动画的要求.在经典质点掸簧模型的表示基础上结合Choi的布料模型,通过简化弹簧弯曲抗力的计算方法,合并了弹簧的结构力和剪切力,从而达到了简化了布料物理模型的目的,提高了模拟的速度.实验证明,采用经改进的质点弹簧模型可以得到实时稳定的布料仿真效果.     

一种改进的基于二重组织织物模拟仿真研究

针对传统的织物模拟方法是基于纱线的圆柱形数学模型设计,只是简单地把纱线抽象化,并没有考虑到纱线本身的属性与光照明暗效应,导致模拟出的纱线表面亮度渐变过快,效果生硬不理想,对二重织物真实感的模拟效果不够逼真,提出了一种二维织物模拟的新方法。从二重组织的构成条件出发,导出二重组织的判别条件,并由此建立纬二重组织的数学模型,从而得出二重组织织物的正反面组织图;再结合纱线模型与织物交织模型,实现对二重组织织物的真实感模拟。实验表明,该方法能够实现真实的二维织物模拟,取得不错的效果。     

布料上污渍效果的真实感模拟

布料上的污渍效果是计算机游戏和影视制作中有待模拟的细节之一.提出一种基于物理的布料上污渍效果的真实感模拟的方法--采用多层模型对布料进行建模.对于污渍在布料上的渗透和扩散运动,提出了NSEAM(Navier-Stokes equations for anisotropie media)模型,它可以模拟污渍和布料之间的相互作用,如扩散作用、蒸发作用、渗透作用等.最后,采用硬件加速的方法对上述过程进行了真实感绘制.实验结果表明,文中方法可以生成不同结构的布料上较为逼真的污渍效果,其绘制效果令人满意.     

A Practical and Hierarchical Yarn-based Shading Model for Cloth

Realistic cloth rendering is a longstanding challenge in computer graphics due to the intricate geometry and hierarchical structure of cloth: Fibers form plies which in turn are combined into yarns which then are woven or knitted into fabrics. Previous fiber-based models have achieved high-quality close-up rendering, but they suffer from high computational cost, which limits their practicality. In this paper, we propose a novel hierarchical model that analytically aggregates light simulation on the fiber level by building on dual-scattering theory. Based on this, we can perform an efficient simulation of ply and yarn shading. Compared to previous methods, our approach is faster and uses less memory while preserving a similar accuracy. We demonstrate both through comparison with existing fiber-based shading models. Our yarn shading model can be applied to curves or surfaces, making it highly versatile for cloth shading. This duality paired with its simplicity and flexibility makes the model particularly useful for film and games production.     

面向不同体型特征的服装款式迁移方法

大部分成衣的设计以标准比例的人模作为参照,而对于非标准体型的顾客,标码 服装的大小尺寸则很难与之进行有效匹配。基于此,提出了一种面向不同体型特征的服装款 式迁移方法。首先,对于一批不同款式的服装,通过物理模拟的方式穿着到标模及非标模人 体之上,形成标模试穿的服装实例及非标模试穿的服装实例;其次,使用仿射变换表示同款 服装在标模及非标模下服装实例间的变形映射,并借助主成分分析法求解服装变形,在保留 因体型特征导致的服装形变的基础上,剔除由服装款式信息引起的服装形变;最后,将服装 变形用于标模到非标模的服装款式迁移,并使用平均离散曲率衡量迁移前后服装款式的改变 程度。实验结果表明,迁移后的服装携带了标模服装的款式信息,并保留了非标模服装的体 型特征。     

基于组织结构的纺织品各向异性建模方法

纺织面料的物理仿真将虚拟现实与纺织CAD相结合,是虚拟服装与试衣系统研究的一项关键技术,纺织品建模也是纺织品真实感模拟的基础及关键工作.在基于物理的粒子系统的基础上,提出各向异性的建模方式.根据织物面料的不同组织方式进行分析,对其进行经纬方向的分离建模.仿真过程分为初始过程的刚性物体模拟和接近平衡时的柔性物质模拟两大步骤.为了在产生逼真表现效果的同时兼顾计算复杂性,构模时引入多分辨率模型.     

Mixing Yarns and Triangles in Cloth Simulation

This paper presents a method to combine triangle and yarn models in cloth simulation, and hence leverage their best features. The majority of a garment uses a triangle-based model, which reduces the overall computational and memory cost. Key areas of the garment use a yarn-based model, which elicits rich effects such as structural nonlinearity and plasticity. To combine both models in a seamless and robust manner, we solve two major technical challenges. We propose an enriched kinematic representation that augments triangle-based deformations with yarn-level details. Naïve enrichment suffers from kinematic redundancy, but we devise an optimal kinematic filter that allows a smooth transition between triangle and yarn models. We also introduce a preconditioner that resolves the poor conditioning produced by the extremely different inertia of triangle and yarn nodes. This preconditioner deals effectively with rank deficiency introduced by the kinematic filter. We demonstrate that mixed yarns and triangles succeed to efficiently capture rich effects in garment fit and drape.     

Interactive virtual try-on clothing design systems

Clothing computer design systems include three integrated parts: garment pattern design in 2D/3D, virtual try-on and realistic clothing simulation. Some important results have been obtained in pattern design and clothing simulation since the 1980s. However, in the area of virtual try-on, only limited methods have been proposed which are applicable to some defined garment styles or under restrictive sewing assumptions. This paper presents a series of new techniques from virtually sewing up complex garment patterns on human models to visualizing design effects through physical-based real-time simulation. We first employ an hierarchy of ellipsoids to approximate human models in which the bounding ellipsoids are optimized recursively. We also present a new scheme for including contact friction and resolving collisions. Four types of user interactive operation are introduced to manipulate cloth patterns for pre-positioning, virtual sewing and later obtaining cloth simulation. In the cloth simulation, we propose a simplified cloth dynamic model and an integration scheme to realize a high quality real-time cloth simulation. We demonstrate the robustness of our proposed systems by complex garment style virtual try-on and cloth simulation.     

三维服装仿真中的"服装-人体"快速冲突检测及响应算法

维胆装仿真可以为三维人体动画生成逼真的服装动态效果，但其中的冲突检测与仿真计算的时间复杂度太高，其实用性一直受到很大限制．提出了一种快速的“服装-人体”冲突检测友响应算法，在人体运动状态下，快速检测服装与人体之间的位置冲突，其时间复杂度仅为O（n）（n为服装模型上的顶点数目）．在此基础上，提出一种合理有效的冲突响应机制，并实现快速稳定的三维服装仿真，取得了真实的仿真结果．     

基于服装款式平面图的三维款式效果显示研究

本文介绍了由服装的款式平面图研究三维款式效果显示的途径,提出了一种非传统的实现三维着装效果显示的方法,即在款式平面图的基础上,结合标准人台的三维数据点,增加适当的服装空隙量来获取款式三维造型点并构造服装曲面,为服装的款式设计提供更直观的帮助。     

Learning‐Based Animation of Clothing for Virtual Try‐On

This paper presents a learning‐based clothing animation method for highly efficient virtual try‐on simulation. Given a garment, we preprocess a rich database of physically‐based dressed character simulations, for multiple body shapes and animations. Then, using this database, we train a learning‐based model of cloth drape and wrinkles, as a function of body shape and dynamics. We propose a model that separates global garment fit, due to body shape, from local garment wrinkles, due to both pose dynamics and body shape. We use a recurrent neural network to regress garment wrinkles, and we achieve highly plausible nonlinear effects, in contrast to the blending artifacts suffered by previous methods. At runtime, dynamic virtual try‐on animations are produced in just a few milliseconds for garments with thousands of triangles. We show qualitative and quantitative analysis of results.     

适于网络试穿的快速三维服装仿真方法

三维服装仿真技术是虚拟试衣的核心,目前三维服装仿真常用有限元技术来实现,该方法仿真花费的时间较长不能满足网络试衣的要求。提出了一种基于服装裁剪分片技术的三维服装仿真方法,该方法参考服装设计知识将待仿真服装划分为若干衣片,然后用贝塞尔曲面分别模拟这些衣片,最后利用纹理映射技术把服装布料的图案映射到相应的衣片,得到服装三维仿真模型。实验表明利用该方法得到的三维服装模型能够把服装的基本试穿效果展示出来,而且所需的时间很短,可以满足在线试穿的要求。     

An Appearance Model for Textile Fibers

Accurately modeling how light interacts with cloth is challenging, due to the volumetric nature of cloth appearance and its multiscale structure, where microstructures play a major role in the overall appearance at higher scales. Recently, significant effort has been put on developing better microscopic models for cloth structure, which have allowed rendering fabrics with unprecedented fidelity. However, these highly‐detailed representations still make severe simplifications on the scattering by individual fibers forming the cloth, ignoring the impact of fibers' shape, and avoiding to establish connections between the fibers' appearance and their optical and fabrication parameters. In this work we put our focus in the scattering of individual cloth fibers; we introduce a physically‐based scattering model for fibers based on their low‐level optical and geometric properties, relying on the extensive textile literature for accurate data. We demonstrate that scattering from cloth fibers exhibits much more complexity than current fiber models, showing important differences between cloth type, even in averaged conditions due to longer views. Our model can be plugged in any framework for cloth rendering, matches scattering measurements from real yarns, and is based on actual parameters used in the textile industry, allowing predictive bottom‐up definition of cloth appearance.