Abstract: Over the past few years, augmented reality (AR) is increasingly diffused among location-based applications. A situation often encountered in AR applications is the partial or full occlusion of – physical or virtual – objects by physical obstacles. Existing outdoors AR applications overlook this issue displaying visual indicators about nearby annotated objects even when those are hidden behind a building, hence, being out of the users’ field of view (FoV). This paper presents a geolocative raycasting technique which enables real time building recognition towards the device’s pointing direction, thereby estimating the FoV of the users. The objective is either to hide or utilize appropriate visual metaphors for occluded objects/locations thereby improving the user’s perception about its surrounding space. The motivation for developing our occlusion handling technique has been drawn from KnossosAR, an outdoors mobile AR guide implemented for the archaeological site of Knossos (in Crete, Greece). We have conducted field trials which provided preliminary evidence of the efficiency, effectiveness and utility of KnossosAR (including the incorporated FoV estimation approach).
Keywords: Augmented reality, occlusion, raycasting, field of view, cultural heritage, archaeological site