Tetsuya Kakuta

Foreground and shadow occlusion handling for outdoor augmented reality

Occlusion handling in augmented reality (AR) applications is challenging in synthesizing virtual objects correctly into the real scene with respect to existing foregrounds and shadows. Furthermore, outdoor environment makes the task more difficult due to the unpredictable illumination changes. This paper proposes novel outdoor illumination constraints for resolving the foreground occlusion problem in outdoor environment. The constraints can be also integrated into a probabilistic model of multiple cues for a better segmentation of the foreground. In addition, we introduce an effective method to resolve the shadow occlusion problem by using shadow detection and recasting with a spherical vision camera. We have applied the system in our digital cultural heritage project named Virtual Asuka (VA) and verified the effectiveness of the system.

Shading and shadowing of architecture in mixed reality

We propose a simple method to express shading and shadowing of virtual objects in mixed reality especially appropriate for static architecture models in outdoor scenes. We create the shadows of the virtual objects in a fast and efficient way using a set of pre-rendered basis images and shadowing planes. The proposed method is limited in interactivity but can operate in near real-time.

Detection of moving objects and cast shadows using a spherical vision camera for outdoor mixed reality

This paper presents a method to detect moving objects and remove their shadows for superimposing them on Mixed Reality (MR) systems. We cut out the foreground from a real image using a probability-based segmentation method. Using color, spatial, and temporal priors, we can improve the accuracy of the segmentation. Energy minimization is executed by graph cuts. Then we remove the shadow region from the foreground with F-value calculated from the pixel value and the spectral sensitivity characteristic of the camera. Finally we superimpose virtual objects using the stencil buffer, which is used to limit the area of rendering for each pixel. Synthesized images of an outdoor scene show the efficiency of the proposed method.

Outdoor gallery and its photometric issues

We have been developing an outdoor gallery system in Asukakyo. Asukakyo is one of the ancient capitals, which is well-known to has lots of temples, palaces and buildings. Nevertheless, most of the assets have been deteriorated after more than fourteen centuries. The outdoor gallery system introduces the virtual appearance of ancient Asukakyo to visitors at the original site with the help of Mixed Reality (MR). To reconstruct the virtual Asukakyo in the outdoor gallery system, it is necessary to handle occlusion problem in synthesizing virtual objects correctly into the real scene with respect to existing foregrounds and shadows. Furthermore, outdoor environment makes the task more difficult due to the unpredictable illumination changes. This paper proposes novel outdoor illumination constraints for resolving the foreground occlusion problem in outdoor environment for the outdoor gallery system. The constraints can be also integrated into a probabilistic model of multiple cues for a better segmentation of the foreground. In addition, we introduce an effective method to resolve the shadow occlusion problem by using shadow detection and recasting with a spherical vision camera. We have applied the method in our outdoor gallery system in Asukakyo and verified the effectiveness of the method.