Virtual Unfolding and Visualization of Papyrus Packages

关于我们祖先的生活和文化的最好的信息来源之一是他们的书面文件。在世界各地的博物馆和收藏品中，有大量的文献，其中许多有几百到几千年的历史，用许多不同的语言和各种各样的书写材料写成。像金属片、羊皮纸、纸莎草和纸这样的片状书写材料经常被卷起来或折叠起来。物理展开这些文件，以显示其书面内容，有可能永久损坏这些珍贵的物品。出于这个原因，研究人员已经开始使用最先进的层析成像技术结合计算工具来访问这些对象的内容，而无需物理打开对象。在卷文件的情况下，这已经部分成功，但需要大量的工作。在所有的书写材料中，纸莎草可能是最大的挑战，因为它的非均匀双层结构。因此，即使是虚拟展开纸莎草卷轴，例如赫库兰尼姆纸莎草卷，也可能是一个巨大的挑战。更困难的是沿着几个轴折叠形成的包的虚拟展开。在初步工作中，我们已经表明，原则上，虚拟展开纸莎草包是可能的，但可能导致巨大的扭曲，使破译脚本不可能。此外，使用第一种方法根本无法展开更复杂的包。因此，我们提出了一种新颖的、基于模型的方法，在这种方法中，整个展开过程由交互式可视化指导。虽然这种方法的目标是最大程度的自动化，但它允许在每个步骤中包含专家知识。这将使纸莎草学家展开甚至非常具有挑战性的（纸莎草）卷轴和包装与高质量。我们不是从3D图像数据局部重建纸莎草图层，而是采用全局方法，折叠双层网格，与实际包的折叠方式完全相同。然后，通过交互网格变形和自动网格图像配准，将折叠后的网格逐渐调整为三维图像。一个关键的贡献将是折叠网格周围的图像数据的交互式体渲染，允许实时响应网格位置和厚度的变化。体积渲染将与网格变形紧密耦合，允许纸莎草学家以完全视觉控制的方式实时操纵网格。虽然我们的重点将放在纸莎草包装上，但这种方法将足以适用于其他书写材料，也适用于其他应用，比如材料研究中的电池展开，或者生物学中的膜或界面等片状结构的重建。

One of the best sources of information about the life and culture of our ancestors are their written documents. In museums and collections all over the world, there is a wealth of documents, many of them hundreds to several thousand years old, written in many different languages and on a variety of writing materials. Sheet-like writing materials such as metal sheets, parchment, papyri, and paper were often rolled or folded. Physically unfolding such documents to reveal their written content carries a high risk of permanently damaging the precious objects. For this reason, researchers have begun to access the contents of such objects using state-of-the-art tomographic techniques in combination with computational tools without physically opening the objects. In the case of rolled documents, this has been partially successful, but requires extensive work. Of all writing materials, papyrus probably poses the greatest challenge due to its inhomogeneous double-layer structure. Thus, even the virtual unrolling of papyrus scrolls, e.g. of the Herculaneum papyri, can be a great challenge. Still more difficult is the virtual unfolding of packages that were created by folding along several axes. In preliminary work, we have shown that virtual unfolding of papyrus packages is possible in principle, but can lead to large distortions that make deciphering the scripts impossible. Moreover, more complicated packages could not be unfolded at all with this first approach.We therefore propose a novel, model-based approach in which the entire unfolding process is guided by interactive visualization. While this approach aims at the greatest possible degree of automation, it allows expert knowledge to be included in each step. This will enable papyrologists to unfold even very challenging (papyrus) scrolls and packages with high quality. Instead of reconstructing the papyrus layers locally from the 3D image data, we follow a global approach by folding a double-layer mesh in exactly the same way as it was done for the real package. The folded mesh is then gradually adjusted to the 3D image by interactive mesh deformation and automated mesh-to-image registration. A key contribution to this will be an interactive volume rendering of the image data around the folded mesh, allowing real-time response to changes in position and thickness of the mesh. The volume rendering will be tightly coupled to the mesh deformation, allowing papyrologists to manipulate the mesh in real time with full visual control.Although our focus will be on papyrus packages, the approach will be general enough to be adaptable to other writing materials but also to other applications like the unrolling of batteries in materials research or the reconstruction of sheet-like structures such as membranes or interfaces in biology.