2012年度 トピックスTOPICS of 2012

                活動報告

JADH 2012(Japanese Association for Digital Humanities) においてインタラクティブ発表

2012年9月16日に東京大学本郷キャンパスで開催されたJADH 2012(Japanese Association for Digital Humanities)にて石川尋代がインタラクティブ発表を行いました。

内容
In this poster presentation, we will introduce a system for displaying digitized rare books, which provides realistic observation by changing appearance of the virtual light direction of the rare book in interactive manner.
Recently some rare books have been provided for public reading as digital data. However, almost all pages are just photographed or scanned as raster images of each page in the books. If the purpose is to read the sentences of a rare book, showing such digital raster images of pages is sufficient for making people read the book. If, however, the purpose is to feel the realistic appearance of the book, we may wish to observe from not only one direction, but also different directions, especially when the book includes pictures, illuminated letters, such as art paintings.
The old books printed in the middle ages of Europe, called "incunabula", were illuminated by handwriting. Such illuminations were painted for initial letters and blank margins of pages. Some illuminations were gilded for making the surface shine as a gold. Such golden shining cannot easily be represented by simply showing a digitized image of the surface of the page, because the golden shining can be observed as change of brightness by viewing from different direction. Therefore we aim to develop a system that enables users to interactively observe such illuminated letters of the rare book from various angles, so that they can feel the realistic appearance of the surface of the book.
As the displayed contents, we choose digital data of the Keio Gutenberg bible, which was photographed in the late 1990’s. The digitizing of a rare book is not easy and photography or measurement is not possible many times. Therefore our purpose is to display illuminations of a rare book effectively by using past digital data (a color image) photographed from the front of a page.
For achieving such interactive display of the Gutenberg bible, we choose iPad3 that has multi touch screen and a high-quality display as a platform of the system. We aim to make users to interactively change the angle and the scale of a displayed three-dimensional (3D) model by their fingers.
The contents that are displayed in the iPad3 are also very important. For the contents, we created a virtual 3D model of the page with color textures. The 3D model is generated by observing photographed images and the bend of a page. Then the bulge of a gilded illuminated part and the printing part are added to the model. The photograph without highlight is used as a texture.
For real-time rendering in the system, some virtual light sources are set, and then display image is generated according to the virtual observation direction. In addition, a specular reflection is produced only to a gilded part by using a specular reflection map with the virtual light resources in GPU.
As a result, we can observe interactively illuminations of the Gutenberg bible changing the direction of a page. Additionally, at the part of gilded illuminations, we can observe sparkle of the surface effectively.