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        目前的服装工业现状依然是大规模生成几个固定尺寸（如S，M，L，XL和XXL）的衣服为主，顾客通过试穿从中选取一个最适合自己的尺寸。虚拟试穿将此过程搬到虚拟空间进行，通过三维人体和衣服模型来完成试衣。本论文面向保衣服尺寸的虚拟试穿，提出了一套基于物理的试穿框架，主要包含了服装与人体的粗匹配（全局配准）和服装与人体之间的穿透修复（细调）两个阶段。这两个阶段又可以进一步细分为人体骨骼获取、姿势调整对齐、服装与人体之间的刚性配准、服装与人体之间的穿透修复，以及舒适度的量化评估等几个阶段。主要研究内容包括

1)  人体骨骼的嵌入及皮肤绑定。对于对称姿势的目标人体，我们采用Pinocchio系统给出的部分解决方案，在其提出的骨骼嵌入和皮肤绑定算法基础上做了修改来使其应用于我们的试穿框架中；对于非对称姿势的人体，我们改进了现有的基于Reeb图的关节点提取算法，设计了更合理的启发式规则并用聚类方法进一步保证了关节点位置的合理性；

2) 人体姿势调整对齐。提出了一种骨骼摆动（Swing）外加扭转（Twist）补偿的对齐方案，将目标人体骨骼的姿势按照参考人体骨骼的姿势调整至一致，通过骨骼驱动的人体变形使得两个人体模型的姿势达到一致。这进一步使得我们可以通过刚体变换将服装模型迁移到目标人体上。具体来说，我们将两个人体模型视为两组点云，通过ICP配准得到刚性变换直接作用在服装模型上；

3) 服装与人体之间的穿透修复。进一步完善了基于最小位移量（MPD）的穿透修复算法，使其更适合虚拟试穿时解决服装与人体之间的穿透。该算法使用离散相交检测（DID）来找出所有的几何相交元，然后借助人体表面的法线信息来确定非法网格顶点。这些非法点最终会以最小的移动距离从人体内部被移出，即最后点到面的带符号距离为零。MPD算法在处理人体与衣服穿透方面，明显优于现有的通用穿透修复算法，特别适合应用于虚拟试穿以及基于实例的服装动画合成等场景中。

        相比于目前存在的虚拟试穿框架，论文提出的方案具有以下优势：（1）对称姿势人体试穿流程完全自动化，不需要手动干预；（2）支持不同体型任意姿势的人体之间的服装迁移和试穿；（3）试穿流程中服装只发生弹性形变，尺寸保持不变；（4）服装的试穿结果最大程度上符合物理规律。

The Mass-production of clothing is still the current status of fashion industry, which prefers to produce garments based on pre-defined pattern sizes(e.g. S, M, L, XL and XXL). Customers choose the great-fitting one by trying on different sizes of clothes while virtual try-on(VTO) systems try to finish the fitting process under the virtual space via 3D body and garment models. This thesis concentrates on size-preserving garment transferring and fitting and a physically-based framework, consisting of two stages: rough garment-body matching as the global registration and garment-body penetration resolution as the refinement, is proposed. Furthermore, the two stages can be subdivided into several steps, including rigging static human meshes, posture adjustment and alignment, rigid registration between body and garment models as well as quantitative assessment for fitness.

1) Automatic character rigging and skin attachment. Rigging a static mesh is far from a solved problem. Thus, we adapted the state-of-the-art techniques to meet these requirements of VTO. To be specific, for human bodies in symmetric poses, Pinocchio system gives a partial solution. Taking advantage of its skeleton embedding and rigging techniques, we make it applicable in our garment fitting framework. For human bodies in unsymmetric poses, we make some improvements upon existing automatic joints extraction algorithms based on Reeb Graph, including more reasonable heuristic rules as well as exploiting cluster methods to guarantee more credible joint positions.

2) We propose a two-stage algorithm, swing alignment plus twist compensation, to perform skeleton posture alignment. After that, the pose of the target body is aligned with that of the reference body with skeleton-driven deformation, which further allows us to transfer garment models onto the target body via rigid transformation. To be specific, we treat two human models as two sets of point clouds and exploit the rigid ICP registration to derive the appropriate affine transformation, which is directly applied to the garment models.

3) We further improve the penetration resolution algorithm based on the minimum positional displacement(MPD) and make it more appropriate for resolving pre-existing cloth/body penetrations in the scene of VTO. It is history-free and uses discrete intersection detection(DID) to find out all intersecting geometric primitives, and relies on the body surface orientation to identify vertices that are in illegal state. These illegal vertices are relocated, with minimum displacements, so that the vertex-to-face signed distances are zeroed. MPD outperforms existing methods for handling penetrations between bodies and clothes, and is particularly effective in contexts like virtual-try-on and example-based garment animation synthesis.

    Compared with the existing VTO frameworks，our proposed scheme has the following superiorities: (1) The fitting process is completely automatic for human bodies in symmetric poses, with no need for extra manual tweaking; (2) Garment transferring between bodies with arbitrary shapes as well as arbitrary poses is well supported. (3) Only elastic deformation is allowed with dimension preserved during the fitting pipeline. (4) The results of garment fitting satisfy the laws of physics at the most extent.