AR-based Visibility Evaluation for Preserving Landscapes of Historical Buildings Nobuyoshi Yabuki* Kyoko Miyashita** Tomohiro Fukuda* * Division of Sustainable Energy and Environmental Engineering, Osaka University ** Hyogo Prefecture ABSTRACT Building tall structures behind an aesthetic and historical building tends to destroy the good landscape. To avoid such situations, public agencies must regulate height of buildings and other structures near the landscape target. In order to check the visibility of portions of high, future structures, in this research, a new method using Augmented Reality (AR) was proposed. In this method, a number of virtual rectangular objects with a scale are located on the grid of 3D geographical model. And then, the virtual rulers are shown in an overlapping manner with the actual landscape from multiple viewpoints using the AR technology. The user measures the maximum skyline-preserving height for each rectangular object at a grid point. Using the measured data, the government or public agencies can establish appropriate height regulations for all surrounding areas of the target structures. To verify the proposed method, a system was developed deploying AR Toolkit and was applied to a scenic building. The performance of the system was checked and then, the errors of the obtained data were evaluated. In conclusion, the proposed method was evaluated feasible and effective. KEYWORDS: Augmented reality, landscape, invisible depth. INDEX TERMS: H.5.2 [Information Interfaces and Presentation]: User Interfaces—Graphical User Interface 1 INTRODUCTION Preserving singular landscapes such as historical buildings, temples, shrines, churches, bridges, and natural sceneries is important. Recently, destructions of good landscapes from multiple viewpoints due to construction of high rise buildings have been reported. To prevent landscape destruction and to preserve singular landscape, regulation of height of buildings and other structures both in and outside of the landscape preservation area can be enforced. In order to properly set the height regulation, it is necessary to evaluate the maximum height that does not disturb the landscape, which is called invisible depth or skyline- preserving height [1] as shown in Figure 1, for all the points behind the specific objects making good landscape. This task is not so simple because the terrain elevations of surrounding area vary from place to place. Conventional manual methods such as manual drawings and using surveying equipment would require much time and effort. Although Virtual Reality (VR) is a possible solution, one must develop a detailed and precise 3D urban model with existing buildings, trees, and other objects. This could take a long time and high cost. On the other hand, we perceived that invisible heights from multiple and moving viewpoints can be evaluated using Augmented Reality (AR) technology without making an expensive 3D VR urban model. Therefore, the objective of this research is to develop a new methodology for building an invisible height evaluation system to preserve singular landscapes using AR technology. Note this method is different from superimposing the virtual designed architecture [2]. 保全対象景観を構成するもの 守るべき高さライン 視点場 高さを規制する範囲 平面図 × × × 視点場から臨む保全対象景観 × × 景観を阻害するもの × × 断面図 保全対象景観を構成するもの 守るべき高さライン 視点場 高さを規制する範囲 平面図 平面図 × × × 視点場から臨む保全対象景観 × × × × 視点場から臨む保全対象景観 × × 景観を阻害するもの × × 断面図 × × 断面図 landscape to be preserved from the viewpoint field landscape composition limit height damaging element viewpoint regulation area plan section Figure 1. Tall structures destroying landscape and invisible depth. 2 AR-BASED INVISIBLE HEIGHT EVALUATION METHOD The main idea of the proposed method is as follows. The user can observe the landscape object under consideration from multiple viewpoints with a HMD and a video camera connected to a PC, the AR system displays gridded virtual vertical scales which show elevations from the ground level and which are located behind the landscape object, on the HMD with overlapped real video images. The user, then, captures the image and observes the maximum height that does not disturb the landscape for each virtual vertical scale. This process is iterated for various viewpoints, and appropriate maximum height for each location behind the landscape object is determined. Then, virtual vertical, maximum height scale models that should not disturb the landscape are generated and the user confirms whether the virtual objects are surely invisible, while walking around the multiple viewpoints and wearing the AR system. A prototype system was developed based on the proposed methodology using ARToolKit [3]. Since the scale of the AR environment is very large, a 900x900mm marker was made. Virtual vertical scale was developed as an OpenGL virtual object. The shape of each scale is a rectangular solid which consists of multiple 5m-depth colored layers. Each layer has different color so that the user can read the height of the scale. In addition, the scale object must be see-through. Otherwise the scales would * Address: 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan. Email: yabuki@see.eng.osaka-u.ac.jp 281 IEEE International Symposium on Mixed and Augmented Reality 2010 Science and Technolgy Proceedings 13 -16 October, Seoul, Korea 978-1-4244-9346-3/10/$26.00 ©2010 IEEE