Embedded labels for line features in interactive 3D virtual environments

Abstract

This paper presents a novel method for labeling line features in interactive virtual 3D environments. It embeds labels into the surfaces of the annotated objects, whereas occlusion by other scene elements is minimized and overlaps between labels are resolved. Embedded labels provide a high correlation between label and annotated object -- they are specifically useful in environments, where available screen-space for annotations is limited (e.g., small displays). To determine optimal positions for the annotation of line features, the degree of occlusion for each position is estimated during the real-time rendering process. We discuss a number of sampling schemes that are used to approximate the visibility measure, including an adapted variant that is particularly suitable for the integration of text based on Latin alphabets. Overlaps between embedded labels are resolved with a conflict graph, which is calculated in a preprocessing step and stores all possible overlap conflicts. To prove the applicability of our approach, we have implemented a prototype application that visualizes street names as embedded labels within a 3D virtual city model in real-time.